V.J.
Your best asset in correcting this behavior is probably your HUSBAND. Bear with me while I explain.
Your son needs to hear from the most significant male adult in his life (his hero DAD) that girls and women are to be treated with respect.
Dad can step in firmly but gently at first and set a no-tolerance boundary for junior.("This is what respect looks like in our family" . . . "If you wouldn't do this to your mom, you don't do it to your sister . . .")
When junior crosses the line, however, serious and consequences need to happen swiftly and WITHOUT much comment! A sufficient comment is: TIME OUT. Just now I saw you do such and such to your sister.
Best consequences: toy(s) change ownership for a period of time, if the toy prompted junior's tantrum. Junior gets a boring, isolated place to play without sis. (Believe it or not, "you don't get to play with sister for such and such a time) really is a consequence for children who only have each other to play with.
Dad's disapproval carries a lot of weight with preschool boys, so this is a critical age for Dad to build a foundation with his son about how to become a real, loving gentleman, which is how you describe your husband.
You are so lucky.
I'm a nanny for a similar set of children, although both children are 5 and 3 now, and "little sister" pretty tunes much of it out and lets it roll off her back.
She's not intimidated by his controlling behavior, so when ignored, he often results to physical attack (pushing her down, hitting, taunting her with destroying or taking a favorite toy, etc.)
On my watch, he is immediately put in a time out chair with a food tray "restraint" During time out, he usually watches HER playing with that favorite toy he had a fit about. When time out ends, he tells me why he is in time out and what he is GOING TO DO NEXT TIME. Sometimes I give him specific things to do next time.
If a toy is involved, she gets to be the boss of the toy for the rest of the day. (She usually shares it with him 10 minutes later, which SO touches his little heart. THEN we talk about the good feelings restored all around . . . . well you get the idea.
Second offense same day: SHE is allowed to go outside to a favorite play area without him or read extra stories with me at nap time or any similar consequence where he misses out on a favorite activity WITH HER.
If injury results from the offense, he is also required to administer first aid WITH ME for her before TIME OUT.
HERE'S THE POSITIVE ANGLE: I keep my camera within grabbing reach, and whenever he allows her to lead or shares a favorite toy for longer than a minute or two, I take a picture of that activity (sometimes even a little camera "movie"), and we make up stories and books with those pictures. Mom and Dad get a bonus: photos of kids!
Sorry this got so long ~ hope some of it is helpful!