Look at teachmetotalk.com for toy ideas DS was same at that age but quite liked ball popper toys, jack in box, cars down ramps, marble runs, hammer toys anything cause and effect. You can then grab the pieces and hold out of reach and he has to ask for it. Don't buy the instruction vids they have free ones on YouTube.
If he likes numbers and letters try wooden inset jigsaws with numbers and letters and he has to ask you for the pieces eg Melissa and Doug or ELC do them (TK Maxx, NCT sales, ebay often have cheap ones). He will probably be motivated to get the pieces to complete it. So for eg just take one piece out and hold it where can see it and model what he has to say 'a' and if he does hand it over. Then expand it so he has to say 'I want ' or 'give me' and build up the letters he has to ask for
You can do this with food too.
He may need lots of practice so we used to break biscuits into tiny pieces so he would have to ask 10 times in a row, the repetition was really important
Does he like tickles, rough and tumble being swung around. DS had few interests at 3 but liked that sort of play so we used that as a reward eg this is an eg of using rewards to encourage speech, sorry it's supernanny but the therapist is ABA consultant. We have used ABA to teach DS. His progress has been slow but steady. He is now 8, in mainstream with ABA support, can read, write and do maths (albeit behind his peers), he can talk in short sentences. But progress varies massively and some children's speech does come in much faster.
If he can label things and do patterns you know he can learn. I would def rec looking at getting some ABA training yourself as that was key for us - learning how to get DS to do what we wanted, teaching him how to imitate and learning how to use rewards / manage his behaviour. Once we had those skills we have used them to teach him everything else and I mean everything from riding a bike, using longer sentences, working out change to wiping his bum.
You can also look at pecs even if you continue to work on speech pecs is a good intro to ABA techniques of rewards and how to expand language again there are videos on YouTube.
Join a toy library if he isn't into toys so you don't end up spending a fortune on things he doesn't like. You can get some cheap light up spinning tops etc which DS really liked. His favourite reward was a free leaflet about a farm (he loved cows!), the flash cards (he often chose work things as rewards) and a singing skeleton from a supermarket Halloween bargain bin (it played a silly song and danced). Look at what he gravitates towards and make a mental note to put away in a box and bring it out when you want to work on language.
While I shouldn't encourage screens poissonrouge is a nice site at that age which is cause and effect and CBeebies has some nice games - sometimes when DS had no interests letting him play on sites like that gave me a break and saved my sanity. Again if he likes them you can use them as rewards for doing stuff you want him to do.
Don't worry about toilet training, 4+ is usual for asc or dev delay. We did it with ABA support using rewards so again if you find a framework which works you can use that as a way of teaching anything.