HVAC inspection leads to $26k estimate for complete overhaul - good price?

The air in my 2100 square foot house is unbalanced, so I called a few highly rated companies to come take a look.

One said I need to close off some of the return vents and convert a few to registers. He wants to place a new central return in the house, moving it from the crawlspace. He says having returns on the exterior walls is insufficient. He also wants to reroute some of my ductwork, rewrap/insulate all of the ducts, and install a new plenum with additional duct lines. Cost: $6000 for labor and supplies.

The other identified a shitload of other issues. Said the wiring was out of code. The condenser is covered in mold. The ducts are wrapped in asbestos. The pipe that vents the furnace exhaust is venting into the crawlspace because the “terra cotta?” is broken. He said the terra cotta shouldn’t even be used anymore because it’s asbestos. The ductwork is mismatched and measured incorrectly. There are only 6 8” ducts for return air with a 4 ton unit, which is apparently bad. Someone attempted to fix the main return thing to the blower on their own and it’s way too small for the amount of air trying to circulate. The furnace is 20 years old and the 4 ton HVAC unit is 17 years old.

He suggested:
- 5 ton 18-seer premiere inhibitor
- Install entirely new ductwork
- Install 95% furnace (heat pump I think?)
- Clean out crawlspace entirely and install new vapor barrier
- Install high quality filter (thick one that is replaced every 12-18 months)
- Install bacteria growth inhibitor
- All code upgrades
- Add two large return vents in the floors inside from crawlspace OR one central return built into closet

Cost with rebates and discount: $26k

This is a pretty big fricking difference in opinion.

Thoughts?