I have missing anims for the crossbows and the Vampire Lord powers don't work at all. I downloaded two days ago, how do I verify ?
Right click on your game in your Steam library, go to properties, then to local files, click 'verify integrity of game cache'.
I haven't had that many problems with DG but I recognize some of the problems OP is having. I've already done a few quests for the vampires but yesterday most of my controls and menus suddenly stopped working yesterday. I can still look around and escape still works, as does wasd, jump, sneak, toggle walk and sprint, but I can't open menus or my map or pull up my weapons nor can I interact with anything (NPCs, doors etc). Dunno what caused, I was walking around and suddenly everything stopped. Really weird.
I also have the bug where I revert back from vampirism after turning into a Vampire Lord and back, so I have to use to console every time to change myself back into a vampire.
I know mods screw up DG and I did have a lot of those, as well as SKSE and ScriptDragon... I'm doing a complete reinstall of the game and play with no mods/third party programs whatsoever, see what happens this time. I am loving Dawnguard so far and I'm gonna finish it one way or another! *triumphant pose*