You are doing the right thing getting him speech services. How long has he been in speech therapy? Do you have a written evaluation from the therapist?
You should have a written eval. Go through it and look up all the terms she uses in it. Figure out what she means, and then ask her any questions you still have.
Do you work with MH at home every single day, twice a day, on his home program? If you don't, you HAVE to start. Speech therapy will not work if you aren't doing it with him at home faithfully, every day. You need to watch the therapist work with him so that you know how at home.
I can only imagine how hard this is with a baby, truly. But you owe it to him. He will be behind in school if he doesn't catch up now.
Be kind and loving to him when he has a toilet mistake. Work up a token economy system to give him incentive to make it to the potty. Maybe a sticker chart, etc. At the end of the week, if he has earned "x" amount of stickers, he can DO something that he really enjoys, like watch a beloved video, or play outside under the sprinkler, etc. Don't tie it to big gifts because that gets too expensive.
For transitioning, everyone should give several warnings that activities are going to change soon. When you want to get his attention, touch him on the shoulder when you say his name. Ask him if he is listening and get him to look at you before giving him direction. When you are working with him on speech work, practice giving him two directions at a time and see if he can do them. Some kids naturally figure this out - others need help.
When he wants something, say to him "Use your words, MH." And wait for him to try. Like if he wants water. "Tell Mommy wah-wah". And smile at him. "Use your words, honey - wah-wah". If he attempts, praise him. If he has a fit, wait the fit out. Turn away from him and wait for him to stop, and then pretend that it didn't happen and try again. Another thing to teach him is "help me". The "h" and "l" are pretty hard, so teach him "ep me". That way, when he is frustrated because you don't understand what he is asking of you, he can say "ep me" and you will know what's wrong.
You are not only working on his speech when you do that. You are working on communication. As he is better able to communicate, everything else will get better.
It is CRITICAL that you really work hard on all of this with him now. If you don't, he may not be ready for school when his twin is, and it will be so hard for you to send them separately. If he has major issues that are uncovered later, you may have to, but right now, work hard on what you CAN do with him.
I wish you much luck, Mom.
Dawn