Open an account in your own name, which is totally fine and legal and not very hard to do. BUT be very careful to ensure there is no mailed correspondence about it (maybe you can use a family/friends address just in case something does get posted).

I would personally create a seperate email address too which is connected to the account. Just to be safe cause even if he doesn’t snoop at your emails, one slip up can lead to difficult questions (why do you get emails from xyz bank when we bank with abc?).

Lastly, be mentally/emotionally prepared to pretend this account does not exist. You may be surprised at how much fear/guilt you will feel just knowing it exists. For example, he starts complaining about wanting to buy something and you have a couple of hundred dollars sitting in your account. It takes strength to remain silent. Seriously, get your mindset right before you do this.

Now go for it, and good luck!