1. DarkAngel said he picked instead of the RNG. There is never a need for random roles; that's simply done because bias is a thing. The only other game I've played without random roles had 5 factions, 40 players, and each player handpicked by the host to be in a faction that they would most probably do their best to make the game fun in. (And no, that host didn't find it hard at all; Mafia isn't exactly hard to host. At all. A t A l l .)
2. If you decide to increase the player-count then the best fix is to reshuffle ALL roles. Whether you choose to do it or not is up to you.
3.
"My laptop can't screenshot" I'm sure it can, one way or another.
"Screenshots are near worthless" Well, that's not true. They can be faked, but they're also the most common provisional evidence around. Just because it can be falsified, doesn't make everything worthless, and your inability to produce evidence for yourself will only draw attention to your own self being guilty.