It is natural to be concerned but with therapy, ABA or other therapy your 5 year old will learn to calm himself down in time. Having a sibling is really very beneficial for your son. My older daughter loves her baby brother to pieces, even though he sometimes really gets on her nerves. My children are best friends and my daughter spoils my son a lot. Since my son has Autism I consider myself very, very lucky to have another sibling to play with him, to constantly hug and kiss him, to just be with him. As we all know, kids with Autism have social difficulties and I really feel that having a sibling and all her friends over here all the time forces my son to interact with more and more people and children. Unfortunately this is what we must do to get him used to social interactions. Have another child, I don't think you'll ever regret the decision.

I don't think there is a one size fits all answer here. It's up to each individual and family. I love my motley crew and wouldn't change anything. I have 5 children total. Two are adults now and the other three are 11, 7, and 4. My 11 year old is diagnosed with autism and my 4 year old is still in diagnosis but are certain he has autism also. It's a lot of work but the reward, for me, is definitely worth it!
I believe my older two and my seven year old demonstrate so much positives for the other two and they are excellent teachers for them. My neurotypical crew has also gained much from these two. They demonstrate a patience beyond their years, have gained kind,understanding hearts. It's been a win-win situation for us.
Talk to your son's therapist if he has one. Ask his\her take on how would be the best approach to introduce this to your son. Talk to your other half, listen to your heart and also your head. There will be tough times ahead either way but as my grandma always said Nothing in life worth having is ever easy.

Well Gabriel is 4 and he has a 10 month old brother. Pregnancy was hard because he didn't understand and would still want to jump and horse
Around with me. But I just had to be alert. Once we had Matthew He does get a little jealous at times but then there are moments when he helps his little brother. I think it's also forcing him to communicate more because sometimes he is getting frustrated. Personally, I had a 2nd child so that I knew when there were tough times that they could support each other. Oh and I don't ever think there is a good time to have a baby you just have to make it work.

From a biological standpoint, fertility drops after age 35 so you could wait until you hit 34 before wanting another kid. I read that the minimum recommended birth spacing is 3 years between births so you could also have a baby now, too. We had no idea our daughter would be LFA. My wife said she probably wouldn't want another kid but a baby brother was born before his big sister's DX. He doesn't have ASD so at least we got a break there.