You've got your hands full, that's for sure.
On my ZX, I went down to factory primer except where there was damage / rust. I body worked each panel, using regular bondo, and then sprayed cheapie aerosol lacquer primer. BIG mistake- the primer was porous, and my bondo underneath got wet in the rain... I ended up having to redo sections of the car where rust returned. BIGGER mistake- in some places I used rustoleum primer... totally incompatible with my PPG primer... more work to re-do.
I fixed my mistakes, and I currently have the car entirely in waterproof epoxy primer. In the spring I'll shoot the color.
If I were to do it again, I'd:
1) sand down to factory primer except where there was damage
2) use a waterproof / fiberglass filler directly on metal
3) spray each panel with epoxy primer, instead of aerosol
4) do plastic (bondo) filler on top of the epoxy
5) spray more epoxy on top of the bondo to keep it watertight
6) use a high build primer on top of that, for guidecoat sanding.
7) color
Re price, I used a budget paint, PPG Omni, and spent $200 or so on materials.
You can see my saga here: http://z.modeltrainguide.com
I suspect you'll be using POR-15 or those other products you mentioned when you get into repairing the floor and subframe. You probably won't use it on the body restoration though.