We tend to hang on to cars until they die, but the question is how do you define "car death"?
Generally, for a utility grade car (nothing special, which applies to yours), I define "car death" as "serious body rust/rot issues that are starting to look structural."
Or, post-crash damage that involves significant frame issues such that a proper alignment is impossible.
Otherwise? Fix it. IMO.
Or until you're sick of dealing with it, but the above is where I would put a car in the junkyard. "Sick of it" or "found a less-crappy car" just means sell the previous one.
Also, our current financial situation would allow us to buy a newish pre-owned or even a new car w/o financing ($85,000 in cash; 1.8M net worth)
Huh. Not what I expected given the car in question.
To be honest, I can't even begin to imagine either myself or my husband doing our own car repairs. I can cook, mend clothing and change light bulbs -- that's about it as far as my "handiness" goes. For my husband, subtract the cooking and add some caulking. I have a hard time even imagining us doing our own painting or home improvement, much less car repairs. I am in awe that people here are that handy.
Buy him a toolset, set him in the garage with a fresh set of spark plugs, a new coil, and a laptop with access to YouTube...
I can do pretty much all my own work, though on rare occasions I decide not to (dead of winter is usually enough to convince me to go pay a shop to do something, or exhaust work - I can't weld). I learned because I had to. My options were fix a car, bike, or walk, and biking and walking weren't options for some of the distances, payloads, or temperatures involved. And it went from there. Being able to do your own work opens up great options - my cheapest cars were $100, $150, $200, $350 (plus a fuel pump), and then up from there, but I lived many years of my life on those cars (in the 2002-2008 timeframe, so pre cash-for-clunkers value screwuppery). And then did jobs for other people for food money.
There's pretty much no excuse for not being able to do basic work on a bog-standard car in the YouTube era. I wouldn't expect someone to start out with clutch replacement unless you had some friends who worked on cars who were easily convinced by a six pack, but plugs and coils? That's about as trivial as you can get on most cars.