No amount of therapy changes a persons basic character and personality, IMHO. He is who he is. Whether or not it's worth putting up with his anger depends on the value of his positive qualities. No one can weigh that out for you. No one on earth can tell you what is, or isn't, a deal breaker. Only you can decide that.

You seem to want to come to a decision that your family will be okay with. You say you have a history of being passive and letting your family decide things for you. Only you can decide whether you want to continue that approach to life. To my way of thinking, this is your life and what your sister thinks has nothing to do with anything. Does she reject boyfriends based on whether or not you like them? The future is uncertain, but here is what is most likely to happen: Your parents will eventually die and your sister will eventually be busy with her own husband and children. At the point, all you will really have is the life you make with the partner of your choice. You'll see family on holidays, but you'll eat, sleep and live with the man you select almost every day for, hopefully, many many years. I think you should choose a life partner based on what you want for you.

How things go when mom and sister visit isn't that important. They won't be staying all that long. What matters is how happy you are being with this man after they're gone.