I faced the same problems regarding coming in from overseas and splitting up the time on a long vacation. Things I figured out/factored in:=================
There is also the matter of the car rental.
I will need a car at least for the off-site attractions but I do want to take the car and return it on wdw property
so I can use magical express to the airport and the early check in for the flight.
These are things I can not do if I book a few nights on UNIVERSAL property.
- If you either start or end off-site, you can't use Magical Express for that part.
- If you only want a car for getting to Universal/Sea World, you can always use a Mears shuttle and still stay at Disney. Lots more convenient, lots less headache. If you are feeling overwhelmed, the less responsibility you have to take with regard to driving etc, the less stress you will have. (That would mean no Universal hotel benefits, though - though we got on fine without them.)
- On a tight budget for a long trip, the value resorts might be the best option. We stayed at the All Stars for less than $100 a night, and while it was a bit cramped (and my son and I shared a bed, leaving the other bed for my daughter) it was fine, since we were at the parks for the most part. At 22 days, that brings your room cost to $2200. Even if you upgrade to a family suite you will still be doing better on your budget.
- You can look at off-site, but a) that means you are back to needing a car, and b) you are out of the Disney bubble. As one adult travelling with two kids and being so far from home, do not over-estimate the comfort of being "safe" with Disney.
Good luck with the planning!