As far as lasting till 4yr. I would think that might be pushing the 35lb rf limit. I have a large kid and hoping to get to 3 rf, knowing 4will be impossible.
I went with the seat as I couldn't get a newborn recline with a radian, but since you are past that, or at,east very close, you might try a radian
You can definitely go more upright with that. Try pushing near wear the baby's feet would be while you're tightening the belt.
I have two lightweight kids and my 4 year old definitely still fits RF, with room to spare. And has a ton of room FF. It's a really nice tall seat and your baby's weight gain will slow once she starts moving.
Alison: BFing, BWing, ERFing mama to KidA (12/25/07) and KidO (6/26/10)