All that should be easy enough.

Do you have the RS232 codes? If you format them in a particular way you can simply import them into NSP3 or post and ask if someone has already done one.

I don't like the idea of controlling the projector via a blaster but that is just me.
The relay would be the hardest part. Can you use a trigger on the pre amp? Integra amps have individually controllable 12 triggers via IR/232 or IP but I do not know about Denon.

One Nevo Connect (NC-50) has 6 ports. You have used 4 ports for RS232, the rest can be IR. A total of 15 devices can be controlled from one NC-50 as you can double up IR devices on one port.

D.