Guerrero
Franco
Bieber
Torkelson
Kelenic
Alvarez
Carlson
Semien
Peralta
May
McCullers
Abrams
Brujan
Adell
McClanahan
Suarez (assuming Euginio?)
Murphy
Pearson
Meyer
Manning
Clevinger
Lowe
Strasburg
Corbin
Heaney
Woods Richardson
Alek Thomas?
Bart
Verlander
Stripling
Hancock
There is my incredibly rough, one minute ranking of your players. The bolded names count up to 20.
In deep keeper leagues with a specific keeper amount, you need to tailor everything to optimize your top 20 through the cutdown. Yes, you probably should trade some of these older guys if you can, but the ultimate goal needs to be consolidating multiple pieces into clear keeper upgrades.
Strasburg for Grayson + Patino + Casas would be a f***ing steal and you should do it immediately, but then you still have work to do because you may not be able to fit Casas into your top 20. You should try to do your own 2-for-1 and 3-for-1 trades to push every bit of value you can into your top 20. Package Clevinger with two good prospects you don't love (say Joey Bart and Nate Pearson) for one rock solid keeper, for example. Identify the prospects you could live without and try to package them up for young core players. You could compete as soon as 2022 if you can convert some of those flimsy prospects into bankable production, because your nucleus seems very good.