The game doesn't work at 500pts very well. It's just not where 40k can really be 40k yet, so glaring problems are going to just happen. If you want to have a Battleforged army, you have to have an HQ and two Troops, so dropping a Scout squad puts you in Unbound territory and frankly, that's not a good start to the game. Unbound is just models, but Battleforged is a coherent army and people prefer to play against Battleforged. If you want Bikes, and Bikes are a very good choice, then bump up to 750pts and you can go from there instead of going Unbound.
So, a problem you have made and a lot of people starting out make, is that you've mixed weapons. This is a general mistake because each gun has a role, and making the squad split roles means that half of the guys can't do their job. So when you're shooting a tank with your Devs and let's say it's AV12, you physically can not roll a 7 to even make a glancing hit to that armor. Let's say you fire at a blob of Nids with that same squad, you have half as many shots as you want to shoot because of a Lascannon and Plasma. Each squad needs to have a specific role and be built for that role only. This is also why I don't put Missiles in a Scout squad, but it's more fine as long as you are just adding the missile to the same target the snipers are shooting at.
Drop the Storm Bolter on the Librarian. You're removing his pistol and that removes an extra attack in Assault. You don't want to do that. He needs two CCWs and a pistol is one of them. It's far more important than an extra shot of S4 AP5. I'm assuming he's in with the Devestators, so I see what the plan was, but it's not worth the loss of an Attack.
Have you thought about Chapter Tactics yet? White Scars might benefit you the most as you go forward if you're looking at Bikes. Not liking Tacticals means Ultramarines and Imperial Fists are basically out, as well as the strong Formations like Demi-Company. You're going to have to pick a Chapter Tactic that gives alternate ways of building Space Marines easily. You still can make a custom Chapter no problem, but their table rules do need to decided from the set lists.