I'm a mum of two ND kids who are now young adults. My oldest DS was 3 when he was first diagnosed so I have been where you are. Our DD was born four years later and was the most awful sleeper, to the extent that a midwife in the hospital said "I now understand why some mums are driven to murder their kids" 😱after she'd screamed the hospital nursery awake all night. I myself became seriously disabled during the birth of our DS and wheelchair bound after DD, so it was very challenging to have children with extra needs.
You definitely need to sit down with your husband and work out a plan to allow you time off and how to balance the needs of everyone in the family. Accept that he won't do it exactly the same as you will but that's also a good thing. Your kids will get different things from both of you and it's important for your DS to be able to bond with both adults in his life and your other child will need some time where they have got a parent who gives them their full attention.
Read up on autism and the different ways to communicate with your child. Meet other parents in a similar situation and find out what works for them. There's not a one way or one answer as all people with autism will be different but there are things that are common and it can make the world of difference. For example we found that an egg timer was useful for stopping fighting over toys because they could predict when they would be expected to exchange/ give it back. We also would tell them a few minutes in advance that we were going to leave or finish something so they would be prepared for the event to happen, rather than it suddenly be sprung on them.
Both of ours would want to know what was going to happen before we went to somewhere strange or different. For example going to the dentist. We would talk about what it would look like, how they would be expected to behave, what the dentist might do and why we were going there. We would role play lying back on my lap, putting sunglasses on and looking at their teeth with a torch, to familiarise them with the idea of being in the dentist chair.
As you discover what upsets your child, you will find ways to reduce them or help them cope. You will have conversations with you DS and I am very certain that he's understanding much more than it appears he is from his responses to you. At 3 our DS didn't say anything at all, no noises when playing and I was worried he was deaf. When he started talking I thought he didn't understand much at all but I was completely wrong. You will have conversations about diverse things and in great detail for things that interest them, be prepared that it won't always be at the most opportune time for you but it's better to be available for them than not. It can be virtually impossible for them to wait to tell you something or lose the idea of what it was.
For sleeping our DD was very difficult most of her primary school years and still has a very strong "night owl" tendency even now. We found having a weighted blanket to be really effective at helping her to sleep longer and more deeply, though it's got to be the right weight in relation to their body weight and I'm not sure how old they have to be before they can use one.
We also used aromatherapy oils and a bed time routine to get her into the mindset of getting to sleep because she really struggled with getting overtired and then highly emotional and unable to switch off.
In primary school years both of our DCs would be fidgeting and finding it difficult to sit still, so they used tangle toys which they could use without disruption to the rest of the class. Having something to manipulate and get sensory feedback from helped to focus their mind.
Regarding bullying, unfortunately it's going to happen. Kids can be very cruel and pick on anything different but a good supportive school will deal with it. Some of it our kids didn't notice, so it wasn't a problem to them. They will find friends in school and play together. Ours both had smaller groups of close friends who they still are friends with. They also have a high proportion of friends who a neuro diverse and can communicate brilliantly with and are very supportive of each other.
Both of them are happy young adults who've done very well academically and been/at university. There are things that will always be more challenging for them but they have found ways to cope with some of them too. So there's plenty of good times ahead for you and your family.