Where to start?

So I'm somewhat new to this but I rather get a head start and work toward change now and be able to enjoy my relationship before its completely ruined. I feel that most of what I'm dealing with is similar to what everyone else is dealing with. Heres some of the things that I'm trying to work with:

He lies and lies and lies some more. I can usually tell when hes lying but he says he lies because the truth would make me mad. 

He's very short tempered and gets very angry or sad within a short notice

It's very hard for him to break bad habits or things that Ive told him not to do (ex. smoking, playing rough with my old dog, cursing in front of my young nephew) 

He gets completely fixated and passionate about unimportant things (his current fixation is getting a loan or saving up for a dirtbike) 

Hes easily unmotivated when some part of a plan falls through (currently trying to go back to school for the 3rd time) 

He was diagnosed with ADHD as an adolescence, just recently he went back on Adderrall but is using a lower dose than he did as a kid. I'm trying to understand that some of his emotions and decisions are fueled by the ADHD but I'd like to see a change. I dont know where to start and I'm not sure what to say to him at this point. It's really hard for me to forget what hes done and I cant find a reason to trust him anymore if hes just going to continue to lie. What can I do to change myself? Like what should I do to make sure I'm not setting off his triggers or how should I handle situations when I catch him in a lie? He has told me he wants to up his dose and Im not sure if that will make things better... any advice is appreciated!