[jotato]

I assume it is fine. The attic was reblown when the heat pump was installed. Rooms don't feel drafty.

I would like to do whole house air sealing. I plan on doing as much as I can myself. (Sealing can lights, outlet covers, etc..)

[toomuchtodo]

I recommend confirming. If your heat pump can’t keep up (“The upstairs is struggling to maintain 65 and the heat pump is running 14 hours/day (I track it in home assistant)”), either it’s undersized, your house is leaking conditioned air too quickly, or both. High level, having a heat pump in of itself isn’t the problem. High quality heat pumps (Mitsubishis for example) will happily extract heat from -30F outdoor air.

(I have a 4 ton heat pump and it will get my 2600 sq ft 40 year old house to temp called for in about 15-60 minutes at extreme ambient outdoor temperatures).