My Dad's personality changes in the evening and it’s affecting my family in a negative way.

My Dads usually not home during the weekdays which means he’s only here on Friday evenings and weekends (because of his job he needs to travel a lot). In the evening he gets really weird and always picks unnecessary fights like once he wasn’t able to open a simple bag of chocolates so I had to show him (that was weird) and then I asked “Can I have some?” He told me no and I should choose something else in our Sweets Box. I told him I can’t because everything is either unopened and we are not allowed to open it (because of my mom) or I can’t it because of my brackets. He started says thing like “Whatever” And “Oh yeah, always the same with you, Talking back...” I tried to stand up for myself but he just interrupted me and said “You win”. He does the same thing to my mom. And every single time he tries to get us to be quiet by saying “You win”. I’m obviously annoyed, I’m sick of dealing with his behavior and I don’t like that side of him. Especially when that’s how he acts half of the time he’s home. Sometimes his eyes are bloodshot and he’s always really tired. He used to be able to stay up intel 12 pm or later but now he always tells my mom he’s going to bed at 8 or 9. I guess that could be due to him getting older but my mom is just one year younger and she’s still able to stay up late. It just makes me sad to see her lonely and trying to enjoy the evening by herself. I looked into him having bloodshot eyes by trying to keep track of him drinking alcohol. He drinks at least two full glasses a night, maybe one and a half. I’m not sure. One other theory I had is that I see him in his room sometimes. Behind a half closed door. Rummaging in his closet or something. Then I head a sound similar to someone opening a pill container. But I never looked into that and I know it’s not polite to do this but I have checked his closet (not thoroughly) and I’ve never found anything. He’s also constantly needing to go in the bathroom.

Another example of his wierd behavior is that he once came into my room and told me to go to bed, at 7:58 pm. I’m 16, almost 17, therefore my time to go to bed is at 11:30 pm, later if I want. So that was complete weird experience for me, because he knows that I’m allowed to stay up for a while. He also gets very aggressive, but not to the point where it’s abusive. Well maybe a little verbally abusive, but NOT physically.

I don’t want to throw my dad under the bus. I love him very much and I’m concerned for his health. I just want my old dad back...

Does anybody have any ideas what’s causing him to change his personality at night?