PS I wouldn't give up on the Darwin if it's something you want to feed. A rotation of various products is best anyway.
You can use tricks to get him to eat it. Incentives like PureBites crumbled on top for instance.
I started with freeze dried too, but (cats) they are all mostly on home made raw now. I do still feed some commercial brands in the rotation.
Another bit of advice, yes it seems overwhelming at first, you mentioned shopping for sales and all. but after a while it all works itself out into a good routine. You'll find the routine may change here or there, but stocking up on meat sales and storing them in a deep freeze is a great way to feed cheap.
Of course you will have to learn how to balance home made raw, but it's not too difficult, pretty much 80/10/10. 80% meat, 10% bone, and 10 % organ meat, with 5% liver and 5% other secreting organ.