I have about fifty tabs in the hatchery and room for about four of those in my stables. Practically out of gold, and while missions are able to cover day-to-day feeding and expenses it's hard to ever save up enough to unlock another stable tab.

I try to go through and release in-between generations that I don't need, but I just have so many different projects going on it's impossible to keep up. Any tips or suggestions on getting this under control?

I've set myself a limit at 8 projects at a time, with one stable tab for each, and I only breed once a week. Those are the personal limits I've found work best and are easily achievable for me, which gives a maximum of it think 160 pets to sort each week.
That's probably completely different for you, but I do think it's important to set yourself limits on breeding
I also find how I manage my stable room helps keep the projects under control, so feel free to have a look if you think it might help you.

You have...a lot of stables! :)

I tend to be a mega-releaser, since I have fewer stables. But one thing that can help with gold is just to feed the "main" stables (for your projects, sales, favorite pets, etc) and ignore the rest!

Also there is a huge discount if you have lots of pets. I use my stable hand and spend under 2l to feed them each day ( wich is nothing compaired to what you earn when you do missions and run the dungeons)