worried my mums bf is abusive/not good for her to be with

I F(20) am struggling with being around my mums partner M(50’s)

I’ll refer to him as SD (stepdad) for anonymity

So my mum has been dating this guy for around 2 years and he lives 3 hours away so they only see each other if one of them stays around the others place. Firstly, I will admit that I’m protective over my mother as she was in an abusive relationship with my dad that I helped get her out of. I fear that she is in yet another relationship with a bully. He makes nasty comments such as when my brother puts on his favourite youtubers/programmes the SD will say “why do we have to watch this crap”. He is also vegan but insists he has no problem with us eating meat but then always makes comments when I eat meat in my own home? Each time my partner and I eat meat without fail he rudely says “eww” at it. Not once have I complained about him eating vegan alternates as that’s his choice! Why come into our house and make us feel uncomfortable when we’re nothing but accommodating?

The SD has also changed massively since they started going out. At first he was very polite to us children and always wanted to help with chores. He recently went to go as far to slate our mum for buying us (my younger brother and I) new air pod pros as the ones she got us for Christmas last year broke and she promised to replace them, neither my brother nor I asked this of her as we’re very grateful of what we have but she insisted. This wasn’t good enough for my SD and told her to just get a pair for herself as we don’t ‘need them’ although both my brother and I are in education and use them daily whereas my mum wouldn’t use them as much (she even said so herself). When I moved away last summer my mum used my room. After I got back the SD made comments such as “oh I miss that bed” even in front of my 11yo brother! She slaved all yesterday making Christmas dinner whilst he sat on his arse and didn’t even do the one simple task that she gave him or help when my bf and I helped.

Earlier this year in January was when he really lost all my trust and respect. He wanted to visit a country he used to live in but could only do so by himself because my mum was working. He rented a car to sleep in which we thought nothing about as he was travelling around the country. About a day or two into the the trip my mum had an odd feeling and decided to check his ex-girlfriends Instagram and lo and behold the ex had posted pictures of places that he said he was visiting. Baring in mind this was an ex that was abusive to my mum over social media and the SD swore he blocked her which clearly wasn’t true as he was now on holiday with her. Each day new posts would come up of places he said he was visiting on the ex-gf’s insta and it was obvious that they travelled all around together. It was only when he got back that my mum confronted him and he admitted that he travelled with her and stayed at her home! He knew he was in the wrong as he would’ve been straight up and told her of his plans from the start. My mum processed the situation and decided to stay with him regardless.

I feel so trapped sharing a tiny 2-bed flat with them as there’s no escape. I wouldn’t be living here right now if it wasn’t for Covid and I do contribute toward the rent so its not like I’m intruding either. Honestly don’t know how to speak to my mum without her getting defensive of him. I’m worried that me being polite has meant I look like I’m accepting of him being here which I am not. Would it be too much to ask if she stays down his instead at least until I move out in a few months? I also don’t know whether or not I’m just being dramatic because he has hurt this family so much. Is it okay for not wanting to be around him?