I'm going to answer your points a little out of order, as it seems like the core of your argument is the first point and then there are some side issues lower down.
Third, and I acknowledge that this is a bit romantic, but for stuff like agricultural work and the manufacture of clothes, food products, furniture, and so on... these are jobs that make people "feel not like they want to die" and "ok with the way that their life is."
How much of your life have you spent doing agricultural manual labor in order to come to this conclusion? (Without any of that capital equipment you're so dismissive of.)
If you really do enjoy that kind of work, in my life to date I have never, ever, seen a shortage of job openings for people to walk beans, detassel corn or pick tomatoes. Some people really do find hard manual labor under the blazing sun the thing that makes them happiest, just not enough people to fill those jobs even after technological progress and capital investment have dramatically reduced the relative number of people needed to do that work.
If "we" decide that "we" all need X, whether it's televisions or vaccines or mink stoles or F-150 supers duty, then by all means, share and share alike to produce for consumption. But if we would rather take it easy (and we would, because excessive consumption under egalitarian conditions is psychologically unrewarding), then we'll all have to share 1 TV in the rec room I guess.
It would appear your proposed philosophy does not make allowances for individual variation in preferences in order to enforce egalitarian consumption patterns.
So if Steve, Cindy and I are the entirely of society, if Steve wants an F-150 and a giant flatscreen TV, he is forced to go without because the majority of society disagrees on the importance of these items, whereas if he convinces Cindy to share his desired consumption patterns, now I am forced to work longer and harder to contribute to producing a F-150 and a flatscreen TV for myself, even though I have no desire to own either of these, in order to keep our consumption egalitarian.
Second, to a large degree so-called "labor saving devices" only supplant labor with energy from coal, oil, or natural gas, so, guess we'll see if anything bad happens because of that (narrator: it did).
This takes an extremely narrow and time-constrained view of both technological improvements and capital investments.
-Consider a humble irrigation ditch and how many trips to and from a stream or well it saves an individual farmer.
-Consider the Erie Canal, and how many fewer human hours and horse/mule hours were necessary to transport goods between the cities of upstate New York after its construction.
-Or a windmill/watermill (the original variety which was used for milling grain). In societies without milling technology and infrastructure, women often spend hours each grinding grain into flour for the bread or tortillas that were the main source of sustenance.
-Even today, you can buy a bicycle which is much faster, lighter, will last longer without requiring major maintenance or repair, and costs less (in terms of hours worked in order to be able to afford it) than a bike from 1950, even though the contribution of fossil fuel energy to the manufacture of that bicycle hasn't notable increased.
First, present company perhaps excluded, it is quite obvious that "labor saving devices" in industry are not actually used to save anyone from labor, as Helen Keller observed in this excellent essay from 1932: https://www.theatlantic.com/magazine/archive/1932/08/put-your-husband-in-the-kitchen/306135/
To the contrary, not only did European workers during the Industrial Revolution work longer hours under worse conditions than did their agrarian ancestors, workers today, even in many of the wealthy countries, are sweating it out for 40, 50, 60 hours per week. Given, as you point out, that globally the fraction of labor which is dedicated to the production of food has declined from perhaps 80% to perhaps 8%, one is apt to scratch one's noodle and puzzle on what that 72% gap of labor has gone toward. In my opinion, the answer is "a lot of dumb bullcrap," but my opinion isn't the only one and that's exactly why democratic control of the economy is so important. ....
One of the things I like most about the great philosopher T. Kaczynski is his observations on how inventions that theoretically improve life actually just become mandatory and make life Suck Ass instead. Like in the abstract it seems like it would be cool to have a supercomputer that you carry around with you but instead what happens is it's 2023 and if you want to buy a fucking chair you have to download the Sittr app to unlock the chair's DLC and conform it to your big fat ass and it's so stupid and annoying! But you just have to do it I guess! That's life!
You keep using "labor saving devices" in quotes when I never used that term. Why is that and who are you quoting?
As for what happened to all the labor that used to be devoted to growing food in the USA, as you of course know, increases in per worker agricultural productivity since the mid 1800s (from both technological advances and accumulated capital improvements) and first allowed society to begin producing a lot more manufactured goods, and then increases in per worker productivity in manufacturing (again from both technological advances and accumulated capital improvements) meant that more and more people ended up in service work where, to date, we haven't seen the same increase in per-worker productivity from capital investments (although we're starting to see examples like self checkouts and robotic chefs which could have that effect in the future).
What all these changes mean is that, in aggregate, the average american today makes enough money in 1-2 years to support themselves for the rest of their life in a style at or above the average american living in 1850.* These dramatic increases in per-worker productivity also mean that by simply moderating their consumption somewhat (and focusing on what spending actually either brings them joy or avoids suffering), many of the members of this forum are able to save enough money in 7-14 years to support themselves and their families for the rest of their lives in a style that makes few if any truly happiness or wellbeing related concessions, an opportunity unavailable to the vast majority of americans for the vast majority of our country's history.
So in summation, if you consider 1850 the pinnacle of human existence, you can live that lifestyle today. If you consider some advances since the 1850s good (say medicine) and some bad (say television) you can pick the good ones and leave the bad ones behind. If you don't want to own a smartphone, or ever pay for a single piece of DLC in a video game, good for you, you can do just that. If you want to avoid humanity and go live in a cabin like the unabomer, you can do that too.
The only thing you cannot do is make the decision for everyone else about what consumption patterns and life decisions are best for them. And even then, you are free to work at convincing people, one at a time or all at once on the internet, that they shouldn't waste their money (and ultimately their lives) buying pickup trucks and giant televisions. Someone trying to do that is why this forum exists in the first place.
*Unfortunately this includes a 1850s standard of healthcare.
