WELCOME TO YT!!
I have 2 cats and when we brought Grayson home it took them a good month to adjust and yes they too did act out. One has made friends with Grayson and the other cat is well tolerating him for the moment.
Give your furbaby time to adjust to his new little sis it will work out in the end. Advice I can give for the peeing everywhere is get him a belly band several people in this forum make them. You can do a search in the search bar and find out more info on them.