Well, it may just be that in the many many many years that the PNFL has been running, defenses have been crafted with the specific intent of taking away the outside run on first down. This is done with lots of point read/zone/run defense logic on the outside, which doesn't help much with quick inside running. Another important thing about inside running you can't do it with a heavy set. The best way to run outside is with a single back and receivers spreading the defenders out wide (since man coverage tends to dominate).
FBPro98 runs fine in windows 7 32 bit for me. In 64 bit, it will run, but the patching executable does not. Best thing to do here is to use virtualization software like VMWare and have a virtual install of something like Windows XP. I know I've run FBPro98 on macs just fine this way.