To help calm him, and put weight on him, I'd get Glanzen 3 from horsetech.com. It's high in b-vitamins, which help calm some horses down, and they can add flavoring (no additional cost) to help get him to eat his feed. The senior feed may be causing him to be a bit hyper... Glazen has a lot of flax in it too, so you can quit the Cool Calories. If you wan to keep him on magnasium, they can add some in for you, so you won't have so many buckets. They only charge for the ingredient, nothing extra for customization.
Heck, they could do a whole mix of flax, b-vitamins, magnesium, an all-around vit/mineral, plus the digestive aid all in one! Email and ask for a price quote. Here's what I would send:
Please quote me on the following custom mixes, all with added sweet flavoring for a picky horse. I want at least 2 oz of flax per-serving.
Glanzen 3 + 2g of added Magnesium
Glanzen 3 + 2g of Magnesium + Pro- & Prebiotics
High Point Grass + enough added Magnesium to make 2g + added flax (for 2oz of flax per-serving)
Glanzen 3 + Photo Finish + enough added Magnesium to make 2g
The High Point Grass supplement has the b-complex in it and digestive supplements.