Top of stairs wood tread to carpet transition level issue
If you happen to have a double-layer subfloor, remove the top layer and build back up under the tread using material of appropriate thickness. 

Otherwise I would make the top tread thinner where it laps over the subfloor. You can do this a couple ways. Either use a hand planer and take multiple passes, or use a tablesaw or circular saw, shifting the fence 1/8" with each pass. Be sure to stop short of where the tread drops down to the riser. 

Either approach has the added benefit of bringing the top rise back to standard. I would still use a small bevel against the carpet to make it easier on feet.

Note that the second option will weaken the tread. The nosing needs to be supported well to prevent cracking. Use shims and construction adhesive to create a solid bedding. 

Regarding Ecnerwal's good suggestion of a full-depth tread extending past the door casing... Those are two different trim assemblies and shouldn't be expected to align. You could nip the corner off the tread at a 45 to meet the casing, though, or simply bevel both the edge and the end slightly and not worry about it. If you're able to get the tread low enough you may be able to leave it as you have it now, too.