Answers (my own, others' opinions may vary)

1. Scratch patterns matter a lot more at lower grits. Once you get into the 8k+ realm the angle doesn't matter as much. In some cases, you have little choice but to hone at an angle. I have not noticed a difference either way.

2. test shave when you think the blade is sharp enough. Usually those who have finishing hones/strops will use them and not just stop at the 8k. They almost always improve the edge further. However, while learning to hone you should seek to get a comfortable edge off the 8k. Finishing hones/strops will generally not improve an edge that is not already sharp (unless you spend a heck of a lot of time on them).