On hours, I think 50 hours a week are unfortunately pretty much standard professional hours and so while I'd like to tell you there are ways to lower that, it may be difficult. OTOH, I personally think 70 hours per week is just flatly unsustainable and will damage health and relationships in the long run so I would only do it for a short period of time (like a big push to get a bonus or promotion) but not long term. So I would work on getting your hours back to your normal pace.
On quality of experience, I would not assume a larger place has its act together more or you will learn more. There is a lot you can learn by helping some place with operational challenges grow and thrive and fix those challenges. At larger employers I always have this sort of "cog in the machine" feeling, where I feel what they really want is like 99% of people to just monotonously execute and only give a shit about what maybe 1% of people (at best) think about anything. I really hate that feeling, and am willing to put up with a lot of ridiculousness to avoid it. Smaller employers are more likely to actually give a shit what you think about things, which can be gratifying.
On the ethics stuff, I would distinguish between garden variety incompetence (part of the fabric of the universe & structure of reality so just get used to it) and dishonesty / fraud. I agree with
@dresden that the person who makes the decision is the one to sign the papers is the right way. I am fine to provide legal advice and have people ignore it. If I'm signing my name to it, it's being done correctly. So you choose, but don't tell me to do something incorrectly and then sign my name to it. One of the few times that it's worth it to just openly challenge your superior (diplomatically).
Don't say "this is totally unethical and you are terrible." Just say, "if I am going to be signing off on this and sending this out, I am not comfortable doing it this way and would need to do that way. If you want me to send the current draft of the spreadsheet so you can review and revise as you see fit and then sign and send it out, I am happy to send it along and turn to Project X." If it was totally unethical, then I might resign but even then I probably wouldn't whisteblow. Not really worth it unless it's like crazy embezzlement or you are an executive or something. But I've never had to deal with anything like that and hopefully never will.
Based on what you described, I'd probably stick it out another six months and see if things get better or whether it stays the same. If you still have that feeling after a year and are still working those hours, at that point I'd jump ship. Nothing wrong btw with testing the waters and seeing what you can get in the market, no need to jump if it's not what you want. Maybe you can put out feelers or apply to stretch job and see what happens while still planning to stick it out where you are for the time being.
