I was unable to edit my previous post as too much time had passed.
I have read all the posts, and like I said earlier you and I are in very similar situations, as it seems are quite a few others.
Fact is though that you can normally make more working for yourself, and have a better time than not.
1- Working at home. You have the option of solving this by working from serviced office space where you are just one company among many. If there aren't any, perhaps that could be a new business venture, even go into it with people in your area that also currently work from home.
2- I think you are right, everything is going mobile. And if you have 20,000 pages built over years of different coding techniques (so not every page is identical in code at least) that is a VERY daunting task to try and convert it to mobile friendly quality content.
Maybe there is someone here that knows of a programme or an easier way than doing that manually.
3- Hire some sales staff. Some people work on commission only basis if you have not got the cash to do that.
4- Slash ad rates if necessary, so you can afford to hire the staff.
I wonder that if you solved those issues wouldn't your outlook be resolved?
In fact I think the mobile issue is the main one. You are right, if you do not have quality mobile content then I think the site won't be as successful as it could be. Even if you get a job you will still need to convert to mobile anyway, you'll just have less time. Or you could sell but then that seems like a shame after you have put so much sweat into the site.
After reading all the posts, I sent out ad proposals. One cannot rely on AdSense, and doing so even in part is too stressful. Much better to have quality advertisers that you can go out for a meal with, help out from time to time as you would in any business.
Good luck, and thanks for starting this thread.