I'd cut out some endurance work (we don't even know what endurance work you're doing? running?) and add in a couple metcons and some more strength. Depending on how heavy your pack is you're probably going to be struggling because your strength isn't all that high compared to your bodyweight. The better the strength, the easier it is to build endurance/conditioning level.
I suppose you could start simulating carrying a pack all day by wearing a weight vest all day.
Sucks about your tendons/grip though. I'd stay away from too much pushing until you can do some good pulling work though.