I’m lactose intolerant so Im on lactose free milk and I find it very hard to drink 4 liters (1 gallon) a day. I try and have 2 liters a day, and I get a big dose of that in the morning with my cereal. You might want to try MCT (medium chain triglyceride) oil its very very calorie dense and I add that to my protein shakes. On the protein you might want to try protein isolates, which is a more refined protein and doesn’t have the after effect that other proteins cause (protein concentrates).
I’ve just joined the Australian ARMY and I’m trying to put that extra 5 to 10 pounds on which I find very hard (currently 180 pounds). But doing this plus what the other members have said you should put on the weight and so will I.

they also sell, single serving nut butters in a tube, those would be easy to carry, just in case you tired of eating nuts all the time.

Justin’s Nut Butter Natural Classic Almond Butter