Okay  the minimally recommended amount, and increase a bit from there if necessary? There’s no good reason to mix all those sorts of things unless you have to stay away from, say, soy.
Crypto Aero isn’t inherently bad, but it’s mostly forage, with some “stuff” that isn’t harmful but is questionably beneficial, and it’s not fortified, and it’s really expensive for what you get. You can do a search on Crypto Aero and decide if that’s something you want to support.
If you have Triple Crown, get the Sr to try, if you have Southern States try the CarbCare Performance.
I’d personally go with free choice high quality hay (with alfalfa if he can tolerate it) and a solid fortified feed fed at least at label directions. Plus/minus tri amino.
1 lb of copra, 1 lb of alfalfa pellets and a vit/min supplement is certainly not enough.
What’s he getting hay wise?
Where I board him cuts their own hay so it’s a local grass mix. He is on pasture 24/7 as well.
My 14yo Luso has a similar issue . Two vets recommended the amino acid supplement Super Sport by Purina. Cup a day. It has made a difference but you know some horses are just built that way.
Of course correct work using that ass will help as well. He’s only 5 so time yet to build muscle.
But frankly he looks like he needs more ( quality) calories to me, sorry.
