AITAH for thinking to breakup with my partner because he hates expensive gifts for my son from my ex?

I am 36f and have a son 12m with my ex. My ex is a surgeon and makes good money.

We divorced when my son was four as he was never available. I work for government job and make decent money. I have majority custody and his father gets like every other weeknd. I get child support which I mostly uses for son's well kept, savings and activities. Also my son visit his father anytime and i never stop him. We live five kilometres from each other and the house where I stay is from my ex in laws. With legal condition, that it can only pass to my son. Also it helps me paying mortgage of my own home which i bought during divorce and it is covered by rent as I rented that house out. So it has been huge help in life.

I started seeing a man , let's say denis 40 m three years back and we got serious. He moved in with me six mnths back with his two children. 14 f and 10 m. We are planning to get married. He is widower and is at great job himself. But issue is my ex makes way much more. And my son studies at international school.

Step kids study at english medium private school too. But my son's school is very different level and denis wanted me to either take my son out or pay for his children school. Which I refused. We fought but sorted out things . It is unaffordable and we can't live decent lifestyle if we pay for it or better to save for their future.

Recently my ex took our son to Europe trip which made denis and his kids feel bad. Also my ex keep giving expensive gifts to my son which i can't stop. I can't just gift 2000 usd worth gifts to each kid

I called him to keep gifts at his home which is casuing fights here. But he told me to buzz off . My son shared things with the other two kids. But they started ruining it. He stopped doing it. Also my son has his own bathroom attached. Whereas other two kids share common. It is also another issue and when I asked my son to switch room with step daughter. He said no. I didn't force .

But denis wanted step daughter to get the room. Note step children have their own rooms. But common bathroom.

This daily arguments in ruining my mind. I love denis and I want to marry him. But his expectations from me are too much and i can't stop my ex from gifting things and trips. My son is only heir to my ex and he doesnt care. Denis and me can afford good cars but no bmws. My son will get such car on his 18th bday from his dad and I see more fights later.

I told my friend that should I breakup? She said you can't let ex dictate ur relationship and need to spine up. And try to make my son live normal life style like other two kids. I don't know what to do. I want one more child and denis is perfect man to carry my family goals. He has his shortcomings. But I feel I will be bad mother, if I stay with him. I want to change him. But he is not understanding

Edit. Adding

Note another future fight I am worried about is that my son wants to be surgeon like his dad and my ex will pay for any expensive medical College if needed.

Step daughter as well want to go to medical College. And denis is saving for her too. But still it is not sure thing , if she doesn't crack medical exams in future and I don't think i can give away 1000s of dollars for her college either. So I feel it will be gonna be other fight.

Aitah?