1) Is additional antispyware/malware still necessary w/CFP? (I would assume so)
It isn't really necessary. Malware can't do much if you block it with the HIPS, tho I'd still use an antivirus and malware on-demand scanners.
2) Can antispyware/malware be ran in active/online mode (eg. Spyware Doctor Onguard)?
If you mean together with CFP3, yes.
3) What active antispyware/malware is known to be compatible with CFP?
I guess most of them will work with CFP3, tho I can only confirm that BOClean, Spyware Terminator's Real-Time Protection, Spybot S&D's TeaTimer and Ad-Aware's Ad-Watch works with CFP3. Best way to find out is to try yourself.