Tried cranking the engine with the newly examined starter reinstalled with just the starter being powered by an external car battery. The engine cranks just as slowly as before; leading me to believe that although everything I've checked on the starter, it's drawing too much current for whatever reason. The engine turns easily with a socket wrench and so the engine isn't seized; but, I think the engine actually turns too easily. May be a result of the decomp cam, but it turns extremely easily, leading me to believe it has very low compression.
The starter likely isn't turning the engine fast enough, but it should still fire over with my starting fluid and spark if it has enough compression. The fuel injector still will not fire under ECU control. At this point, I'm not out anything as I haven't bought it from my friend yet. But without progressing any farther, the scoot already needs both tires replaced, both wheel bearings, brakes, CVT belt and needle bearing at a minimum. Even if it was running, this has made it more economic and laborious trouble than I'm able to dedicate at this time.
Likely, it will simply be parted out now. So if anyone's interested, it's basically a complete scoot and most everything on it is functional. Sensors, seat, switches/controls/levers, cluster, body panels, etc. Thanks to everyone who replied; I'll keep you all posted!
2004 K4 Burgman 400