Not sure what to do.

My mom’s been married to my dad for over 25 years, it’s not a very successful marriage. Each day mom tells me that she wishes she chose someone else. They’re still together, mainly because if mom divorced dad, she’d have no place to go, since the house we live in was paid for by dad’s parents and all, so it belongs to his side of the family more than ours.

How does this relate to your story? Well, mom’s friends have been telling her all the time that going out with and marrying that man is a mistake, that nothing good will come out of the relationship.
Mom told them they’re wrong, but in reality, they were 100% correct about him. Nothing good came out of it, mom wasted 25 years of her life, father is a fat slob and a pain in the ass, and I, the effect of their romance, am a 21 year old male loser with no future.

Should I mention he is just a low-paid security guard and one of mom’s other admirers is now a university lecturer and a writer? She should’ve listened.

So yeah, you might not see his flaws, since you seem to love him, but if your closest friends tell you that there’s something wrong with him, maybe you should really, really look into it.
Players in general have ways of making girls feel special due to their experience with various women, from what I know, depressed, suicidal girls and girls with low self-esteem are the easiest targets.

Don’t let yourself be fooled, if he turns out to be a player, he’ll dump you once he gets enough sexual favors out of you and you’ll be in ruins because you trusted him with all your heart. I’m not saying it’s not okay to trust him – you just shouldn’t trust him TOO much when there’s a sliver of a chance that his intentions aren’t completely clear.