Hello
I have worked with autistic adults for the past seven years, and have experienced many of the same kinds of tantrums (or what we call "behaviors") that you are describing. And it is really hard when it isn't a light, tiny two-year tantruming!! I think it is for the same reasons though...two year olds tantrum because they do not have the words to express themselves, but they frequently stop as the acquire better use of the language. When kids (and adults) still cannot use words to express themselves, they continue to communicate through behaviors. We do a variety of things at my work, depending on the person we are serving.
Do you have a system (pictures, faces, ????) that you use to communicate with Justin? Or does he speak well enough to verbally communicate? I was thinking that maybe teaching him to use smiley faced/frowny faced cards/other feelings cards might be helpful??? Or giving him some other way to communicate with you when he gets really upset?? I am sure that you have already tried something like this, but if you keep trying, it might eventually work. Also, maybe you could do a picture schedule each evening, so that Justin knows what to expect. It could be on a board, or even something that he can carry with him and cross off as he does it.
The other thing that seems to be really effective is some sort of reward system. Is there anything he really loves that you could reward him with if he is able to get ready for bed without a tantrum several times in a week? Or a special place he likes to go? It seems like giving a tangible reward (like a sticker or a smiley face) each successful night is a HUGE positive reinforcer. And having a bigger goal to work towards can be very motivating!!
Good luck...I hope you get many more good ideas!
Christy