If I were Garcia, I'd accept this fight. He doesn't need to demand too high a paycheck for this. It is acceptable to be given the smaller slice of the purse. After all, that share is still high enough, as you've said, might be his largest ever. Not to mention that he is able to fight against a legend who is already slowing down with age. Although he is not in his best form himself, Manny is definitely a lot older than him and has been inactive for a while.
Garcia's market is lower compared to Spence and Crawford, so he should accept this fight, not because of the opportunity to earn but to beat Manny, as the moment it will happen, his value will also rise and next fight, he can demand his price.
I'd be very happy if Manny is the underdog in this fight. My money goes out to him as well.
That would not be possible, Manny will be the favorite but only a slight favorite.