i'll just abandon the site and take whatever residual income it may produce

I have successfully done that ever since 2002 which was before AdSense was even invented.

AdSense and other affiliate programmes still cover costs with more than a sop for a cup of coffee left over.

I know that, for 2017, the sites I have done the least amount of work on, and have paid very little attention to, have been more steady and productive than those getting all of my attention. I've also made the recommended changes to sites and have seen little return for the work - Google must like watching webmasters jump through their flaming hoops! ; )

Depending on your traffic volumes and geos I would suggesting looking header bidding to compete against AdSense to force a lift in eCPM rates...

This is the last time I'll be re-vamping my site ... The site is over 10,000 pages and i'm not going through it again to make it AMP compliant. Everytime Google comes up with some new thingy to do to a web sit to make it "better" it takes me over 3 months of hard work to rework the site and i'm not doing it again.

AMP is entirely optional, and not necessarily beneficial depending on who you ask. If your site is responsive and fast loading, you probably didn't need to worry about AMP.

Are you by chance changing URLs with the "re-vamps" you do? You don't want to make drastic changes to the site including URLs unless you're a HUGE brand site, otherwise it can take a really long time (if ever) to recover if you don't do things properly.

I've been with AdSense since the beginning and I make site changes to benefit users, not appease Google. I have done maybe 2 redesigns in the last 15 years and I try to never change URLs unless there's no other choice. My sites are responsive and I don't care about AMP because I use CloudFlare (CDN & more). I'm still doing well, I try to not touch things really in general unless they're needed.

If you don't want to do endless ad placement testing you could try something like Ezoic. It uses AI to place ads all over the place to see what works where and with who.

I use Ezoic on two of my sites, it improved revenue on the one but I only saw a marginal improvement on the other. The rest of my sites I just use standard AdSense responsive units. I probably should do more testing.

In the several redoing of my website over the years i've never made drastic changes to pages (URLS), usually just design changes.
I'm just trying to find out why the drastic drop in income, and what I might be able to do about it.

Thanks
Satchmo

We really can't recommend any particular ads. What works for one site doesn't work for others.

How much change was there in terms of ad placement from the old design to new? Maybe you're losing money because AMP typically earns less $$.

Do'n't change from 336X280

Maybe i should change back to non-responsive design.... When i made the changeover is when a lot of the stuff happened. No AMP on my pages.

@satchmo I have jumped through every hoop that Google said I should jump through except for AMP. Every improvement only made things worse. For example, this morning my CPC is at 0.00. AdSense has turned into one hot mess. My days of trying to please Google are over.

Yah, 2017 was all about modifications/changes to all my sites and the results, so far, have not been positive. Use to be that people made the internet what it was, now Google is shaping it into its own image.

Build your site for users, not Google. Put up a survey asking for feedback from users for a week and see what they say.

There is a downside to this though, especially since i've been paying my writers from the proceeds from adsense, no adsense income, no website...

Maybe your site was demoted due to an algorithm update.