I like to think that Lance genuinely loves his entire family (his "father" isn't family), and wants to have healthy relationships with them and listen to Frederick's rants about his books and encourage Blaine to pursue theater, like Lance KNEW he'd wanted ever since Blaine was five even if Blaine didn't know, and all that stuff, but he was too scared to Leland to do any of that stuf. So he just played up his "goofball" personality to the point that it basically wasn't Lance anymore (if Lance wasn't acting for his father I feel like he'd give Kaito Momota x Giovanni Potage vibes), and tried the best he could to give his family what he wishes he could give them.
He knows it isn't enough though.
He tries to hug Frederick and give him all the physical affection that the rest of his family refused to, but all he gave Frederick were even more bruises than Blaine and Leland already gave him. He wanted to help his brother out of his depression, and encourage him to do things and HELP, but Lance couldn't. He wanted give Blaine a break from it all where he doesn't have to be perfect, and encourage Blaine to embrace himself, and separate himself from Leland, but it was never truly enough.
So yeh, Lance is definitely the first brother to rebel against Leland
