On party nights it's rough getting back into the park. In all my times they let the party goers come in starting at 4 pm even though the party starts at 7 pm. They are herded towards Fantasyland. You could run into the beginning of that crowd coming back and it's a zoo.
With Liberty Tree Tavern you would be in the back of the park; that's the best place to be when the party begins. Why give that advantage up?
I believe if you want to enjoy the party I don't see the sense of wearing yourself out with this commute. I don't find that relaxing. It's a late night doing the party well; so, stay put. Take your meal real slow at LTT and get a rest that way. I wouldn't rush out; because, you have the 3 pm parade happening while you are eating. When done with your meal do something relaxing like taking in the Hall of President show or the Riverboat ride or both that's near by. This will let your tum-tums have a chance to digest their meal. Don't forget to get your wristbands for the party or whatever they use for it. There are different locations throughout the park to do it.
The party gives you cookies, cocoa, and fruit (probably apples) to enjoy included in your ticket. To me, that's enough to snack on. Make it clear at late lunch, early dinner at LLT that this is the main event of the day for eating.
A few snacks will be ok if you want them, too. I think there's a place where you can get soup as a snack credit in MK. That might feel good as the night gets colder and colder.
I've done the party many different ways myself through the years and I wouldn't leave the park.