For starters, I don't actually agree that Lucas' first thought was to go in and save Peyton...he actually went to stop Nathan. But I'd happily argue that when he realised how adamant Nathan was to go in and get Haley, he realised he needed to do the same for Peyton...but still undecided on that.
However, he didn't come out to be with Brooke. He came out to stop Peyton from dying. He might have been with Brooke when he came out and hugged her, but the way you said it, makes it sound like that his was motivation for possibly facing down Jimmy. And it wasn't. It was because Peyton was unconscious and was going to die if he didn't. I don't mean this in a mean way but I really don't think he even thought about Brooke in that moment.
I'd also contest that their (BL) time together wasn't about Peyton. My one issue with BL is that it was far too much about Peyton (and the insecurities that sprung from that, which may have been founded upon something very very solid but Brooke made the decision to take him back...). But at the same time, and you can ask soulunsung about this lol, I really do appreciate the BL relationship. Sure I have issues with them and I never saw them as being endgame but I still enjoy them together.
And Peyton wasn't with Jake. Jake had left. I mean, she was clearly still like in love him with whatever but they weren't a couple by any means. I think she was closer to being with Pete at the time lol