Underdog Tactics , Guild Representatives, and crew size/reinforcements

1. I'm running a scenario with a friend as part of a dominion campaign and im rated 1700 and he's rated 1000 so he'll get some underdog tactic credits to spend. He wants to get two brutes with those underdog credits. Our scenario is meat harvest (#42) and it uses the following for crew selection:

"This scenario uses the standard rules for choosing a crew, as described in the Battlefield Set-up & Scenarios section of the Necromunda Core Rulebook. Both gangs use the Random Selection (D3+2) method to determine their crew. The rest of each gang's Fighter cards are shuffled together to form the Reinforcements decks."

we havent really played any scenarios so far that use reinforcements or random crew sizes so im not sure how these interact.

Does he get his 2 brutes on the field in addition to his d3+2 gang members because they arent considered crew? Do they go in the fighter card deck and get randomly selected to either be on the board at the beginning or in the reinforcements deck to come in later?

2. I also ask because im thinking about joining an alliance (house van'saar + promethium guild) and possibly bringing the guild representatives. Do they work the same way as the brutes above?

3. How do reinforcements work exactly? it says at the end phase you roll to see how they come in. you roll a d6 and depending on result either you or the opponent place the randomly selected fighter? Do you do this for every single reinforcement in the reinforcement deck for both players?

Sorry i know thats a lot of questions but i'm hoping someone can help