My machine chokes on FPSC stuff too, so I feel your pain. My future son-in-law showed me a site where I can get a state of the art gaming machine (or rather, the parts to build one) for around $700. SOOOO tempting... darn him, he'd better build me one if he wants me to pay for his wedding to my daughter in a couple years.
But I digress.. I try to keep the rooms small and only use dynamic entities when *absolutely* necessary - most of my scenery is static, including lights.
You can have many rooms and not impact performance too much if you use trigger zones to spawn your entities as you go, then remove them when killed rather than have them all up and running at once, and laying around dead all over the map afterwards. I also go into the setup.fpi on my final builds and turn off post processing since bloom tends to look like crap on my machine anyway, and isn't worth the performance hit I take whenever it's on.
It compiled! Ship it!