Navigating insulation, mold, and air quality issues

I'm pretty confused right now because there are so many different perspectives and prices when it comes to insulating a home.

A few notes on what's going on:

1) There's a recurrent mold issue on our bathroom ceiling. I've cleaned it multiple times but it keeps coming back. A mold specialist came out and did an inspection of the entire home. He said it's crucial I get my insulation issues under control and then he would come out and clean the mold.

2) My electric bills on a single story, 2100 sq ft home hit around $450 from June through September. We purchased a new high quality HVAC/furnace system and installed and rerouted new ductwork in 2021. We also have zones installed. While the system works really well and can make sections of the house really cold/warm when needed, the house is drafty and some parts do not cool or heat efficiently. It definitely doesn't maintain temperatures and my son's room can hold 68 for a while and my bedroom (on the same zone) will dip to 62.

3) Around 33% of the attic isn't even insulated. Previous owners removed it or moved it around for some reason. There was an extensive roof leak years before we moved in and the existing insulation is damaged. There's also an old non-working whole house fan with zero insulation under it.

A national company says we need to remove insulation, do a home air seal, install new fiberglass insulation (R38) and install a solar powered fan.

Here's their quote:

Removal AND disposal: $2000
Home air seal: $750
Attic hatch cover: $150
New insulation: $2000
Solar powered fan: $1500
Removal of whole house fan and sheetrock replacement: $1600 (independent contractor)

Discount for doing entire project: $750

Total: ~$7700

A local company says most of that is unnecessary and here's their quote:

Removal: $2000 (I have to provide the dumpster so add in what? $500?)
New insulation (R30): $2400
Removal of whole house fan and sheetrock replacement: $1600 (independent contractor)

Total: $~6500

Ok, so go with the national company, right? Seems like a deal to get higher graded insulation, a fan, an air seal for $1200 more.

But then I go online and read that home air seals can be really bad for air quality because if the air has no where to escape, then it can cause issues. Also, turning on exhaust fans (bathroom, kitchen) can create negative pressure. Being on top of an unsealed crawlspace, that negative pressure can bring up air through the floors leading to elevated radon levels.

So don't do the air seal, right?

The mold specialist said the main reason the mold is building is because there's a draft between the attic and the house causing condensation when the temperatures are drastically different. Doing all we can to prevent air transfer between the two spaces is the best way to prevent the mold from coming back.

Ok so do the air seal?

A third company said they wouldn't even remove the old insulation and that it was an unnecessary expense. They suggested I do it myself to save money because it would just be the cost of the dumpster.

I'm confused. Any suggestions?