You sound like you love your bike already
Let's sort it out........
Your rear brake is made 'crap' from new. All the XB's have a soft rear brake due to the short wheelbase and strong front brake. It's so you don't lock up the rear and lose control.
The noise from the front screen is the horn vibrating inside the fairing. This is extremely irritating, so my fix was to remove the screen, (just pulls off), remove the front cover and look for away of altering the horns position. You can try bending the bracket, but in the end, I drilled the horns' bracket halfway between the horn and existing hole, (to change the vibe frequency), turned it round and 90 degrees up or down, (to make it fit back in the fairing). Anyway you get the idea.....
By 'vibey engine' do you mean poor low speed control, or just 'thumpy'? If it doesn't get better, or gets worse, you may need to carry out the 'TPS HARD RESET' in the 'How to' section on the forum.
As you are new at this Buell lark, you will find that they are reasonably high maintenance, but the Uly will reward you in spades with it's 'I can do anything' design.
As for doing your own maintenance, you will need quality tools of the AF/Imperial type, Spanners, Sockets, Allen keys and a good set of Torx's bits-make sure you get a T27 for the bodywork, this one is normally separate from boxed sets. You will also need a torque wrench for tightening wheels in particular, if you can afford one get one that does left-hand tightening for the front wheel.
One other thing you will need for diagnostics and various operations is a downloadable software called 'ECMSpy' you will need a cable to connect your bike to a laptop. If you do some searching on here you will find out how to sort it out.
Anyway, good luck with the bike, and don't be shy with any questions!