I'm working through some similar questions for our trip next March, so this thread is helpful for me too!
The one other thought I'd mention that I haven't seen yet, but that I am including in our lists...if staying off site saves us a ton, we can put some of that money into improving our trip experience in other ways. Maybe EMM or a fireworks dessert party, maybe a special tour or package somewhere, maybe an extra character meal, etc. So as I go through and make our lists and consider EMH vs off site, I'm going to try to figure out how many of the things we EMH would allow us to do are experiences we could also pay for, and compare the extra costs there vs the extra cost of the room on site.
I suspect we're going to end up off site, because we have a grandmother coming as well and the extra space of a condo would be nice--I'm looking at 2 bedroom DVC villas as well but even with points rental most look too expensive. Also if we do WBC I can save money on not doing a water park day, plus the savings on food, etc. But on site sure is tempting with EMH.
I'm also going to keep an eye on park hours for the same period this year, too--like you we wouldn't use evening EMH, it's too late for us. Mornings we would probably use unless its crazy early--we had planned to use the 8 am EMH at AK recently but they moved it up to 7. We made it there about 7:30, and it was fine, but realistically I'm not going to get everyone up and organized to rope drop super early EMHs regularly. I know there's no guarantee that next year's hours would be the same, but it's the best way I have to predict things!