Time to answer these to the best of my abilities...
Press O to lockon target/ Reset Camera (as in making the camera facing in the direction your character is facing. If you need extra help moving the mouse to aim, consider downloading this mod to help. It should smooth out the mouse and make camera control easier. Mouse Fix
Press V to switch the right weapon and C to switch the left weapon/shield/catalyst. Also, press F to switch items and R to switch your magic you have attuned.
As for this, just keep in mind that for PVE, you should be fine as long as you can accept that the game is going to be hell of a lot harder for you. PVP, good luck. PVP is going to be a mess for you, mainly because controllers in this game have a LARGE advantage over Mouse/Keyboard players. If you plan to main PVP consider investing into a controller that you can use.
The PC controls in my opinion are an absolute failure. Now, I am not bashing the game being bad, just that the developers did not intend players to use PC controls. Although, I am sure that if you are skilled enough, you can beat the game.
Now last note, what you currently do is good practice, but for bosses try to predict their patterns and dodge them. Dodging, if done right, should be more effective than pure blocking because it should leave more stamina and let you have more control of the fight unlike blocking and then being limited to only more blocking or rolling away to heal.
Unless you use a pure strength build and withstand the damage dodging should be a better choice.