Well said. If you hit a vein, however, you will likely not see a bubble but rather a slight trace of blood seeping back in (not to mention more pain than necessary).
It actually isn't so bad.
You really shouldn't flex while injecting, for a number of reasons. I would not recommend that.
I think by "feel" he means the effect of the Testosterone in the blood stream in relation to work-out, libido, etc. This is usually 10-14 days for Test E (at least in my experiences). Other people contest that it's as much as 4 weeks, but I frankly find that untrue.
This is very subjective to your own experience, mazilla. Not to undercut good advice, but it's not necessary to eat beforehand, nor is it entirely necessary to wear gloves so long as his hands are thoroughly clean. As far as passing out, that's only about a 10% chance that varies from person to person.