Cap question

[BeastsoftheNFCeast]

I'm trying to see what moves the skins should/could make in terms of the salary cap (ie what players to cut, whose contracts can be restructured and to what extent, how much money we can spend in FA, ect). I have a few question about the cap.

1. When a player is put on IR, and a new player is signed to the team, what money gets counted towards the cap when a new player is signed? Lets say if someone with an 8 mil hit gets put on IR with 8 games left in the season, and someone else signs to a .5 mil contract. Is the hit towards the cap that year 8.5, or does only the IR players signing bonus that year get counted, or does only the percentage of games that he played get counted, or whats the deal with that? Also, it seems kinda unfair that someone who gets paid .5 mil is on the team half the time and is worth less than someone who mad the team in the beginning, do they really get all the money?

2. Hypothetically, if enough players get injured, is it possible to not be able to sign more players because you will go over the cap?

3. I have truely only followed football very seriously for about a year now, about how many players contracts are restructured a year, and how much is saved when contracts are restructured (I know this is a broad question, but if someone could give 2-3 examples, that would be great)

Thank you