10.5 and medium sounds like it might work. Kinda on the edge of med and large, I reckon.

Pretty much want the ball of your foot near the pedal spindle. I like a little more insertion personally, ball of foot a tad forward of pedal spindle.

Varies by pedal cage width for me, and by width I mean front to back. Fatty MTB pedals I need small for my size 8s, slimmer track and quill road pedals gotta have med.

PD-1050 pedals I like med clips, but they ain't yer average clips.

Once I had monsterous MTB pedals and huge clips and had to wrap a buncha tape around the toe bits of the clips to keep from feeling like I was in too deep.

Oh, and depends on shoes too. Slip-on Vans 24/7/365 then you might want a size smaller than if you're wearing thicker shoes. I got puffy Vans that fit WAY different in the clips than ye olde slip-ons. When I wear steel toed boots on a bike with clips it's just plain, um (word you can't say).

OK, last edit I swear. If you do a lot of low speed tight turns or are otherwise plagued by yer toes hitting your front tire, then try a size down.

Ummm, one more edit while I'm waiting on a download. Depends on clips too. some clips have the two prongs closer together so they'll act smaller depth-wise than clips with wider spaced prongs, so considering all that, there's no magic formula.