The clothes issue is most likely sensory processing disorder. My oldest has this.
It's so so so much harder for my oldest in the winter because of the extra clothes (especially shoes and socks). And she didn't wear underwear for a long time. And she's not wearing socks now, will only wear one or two pairs of soft stretchy pants that fit "just so," and will have fits over her shoes. To top it off, what does and does not work seems to change relatively often. One day she'll wear a pair of shoes and the next she can't handle them. ugh. Very frustrating for both of us. Just keep in mind that his brain handles the input differently and he really can't help it. And, I'm told, it gets better when they are older.
In the meantime, try to find an Occupational Therapist (OT) who works with sensory kiddos. We sent our oldest to one for around a year. It helped with bigger issues (whole body movement), but not as much with the clothing issues. Then again, we stopped doing the follow up therapy (e.g., brushing arms and legs with a surgery brush and doing joint compressions) during a time she seemed to be doing better. So, we could probably be more vigilant with the home therapies and help her more.
Good luck!