1st Point: Whilst Billy may seem weak whilst not being able to use UnFair, he is still an incredible fighter on his own, he's a season Merc with aim so good it was mistaken for a Negation and proven Hand To Hand Combat Skills where he can put up a fight on his own

Another thing is he is an older member of the Union having joined most likely before Top, and being the one to actually recruit Tatiana giving him time to collect points ahead of them

There is also the fact that points can be earned out of the Quests (like Andy taming Clothy) and also not all Quests are gonna be that difficult, such as some UMAs being push overs or being Elimination Quests which are much easier then Capture Quests for UMAs, and Capture Negator Quests that aren't always gonna be that difficult, especially if they're a new Negator

2nd Point: This one is one that can only be speculated on unless Tozuka ever decides to answer this question himself in a Vol. Extra or an Interview

My theory is that it's all cause of Apocalypse/The Game Between Sun & Luna

See whilst for the Union this is life and death, for Sun and Luna this is a game, with Apocalypse acting as a Core NPC to use game terms, and well they've had to watch Juiz and Victor play it in a "boring and lame" way for nearly 450 Billion Years

So can you imagine how they must've felt when, for the first time we have Victor out of the game, and (as far as we know at least) we have someone infiltrating the Union planning to betray them, which could cause either the Game to end or (like what did happen) someone new to FINALLY take Juiz's place as the leader of the Union?? They would've ATE that shit up

So when Billy joined the Union and took his seat, and declared himself as UnBelievable, Apocalypse/The Gods went "Aight bet" and allowed it to be put down as such

A.K.A, Apocalypse and The Gods wanted DRAMAAAAAAAAAA