Aw, mate. It is soooooo tough.
It is a period of adjustment, as I know you already know, and it will pass. There are odd occasions when N is still aggressive toward P. And it has been 17 months since she came into our lives. I have really struggled to show N positive attention over that time and TBH a lot of the time it has to be a conscious decision to love her.
Gosh, that sounds horrible! Sorry.
However, I look at the bond they share and the way N has taken P under her wing, is teaching her things and shows pride in her, and I have to say it is all worth it. Jealousy is a part of sibling relationships IMO, and I reckon it's an unusual blessing to not have to deal with it in a family context.
Things are going to get better soon. DS2 will settle down and you will have more time to spend with DS1. DS1 will adjust, and while I am sure there will still be unavoidable jealous moments there will also be lovely moments. You just watch, I'll bet your DS1 gets the BEST and MOST ENTHUSIASTIC laughs from DS2 than anyone else! Once DS2 is more interactive DS1 will be more aware of him as a person rather than a noisy thing that is taking mummy's attention away at the present time.
Do you have anyone around who can help when DS2 is unsettled, to maybe take him for a walk or wear him in a sling so you can spend a bit more 1 on 1 time with DS1? That might help too.
All the best - things will brighten up