1) Whatever.
2) Whatever makes it look right on the ground glass.
3) Yes light got in. Jamming isn't normal.
4) Good
5) A little wiggle is normal. After developing, use sheet from question 3 to practice loading in the light.
6) Meh, so what. All that counts is clean.
7) Yes f/8 is f/8 is f/8, but you have to do the math.

f = focal length, the real focused focal length not the marked focal length.

If the marked focal length is 210 then f=210 at f/8 is 210/8 so aperture diameter at the f/8 mark is 26.25

If the marked focal length is 210 then 210 is where it focuses at infinity.

If you extended out to say 315 that means 315/26.25 = 12 so f/12 at the f/8 mark

If you extended out to say 420 that means 420/26.25 = 16 so f/16 at the f/8 mark