3yo with suspected SEN - school can't cope, help!

[Frenchmartini02]

We are overseas, DS is 3.5 & moved from creche to montessori pre school 4 months ago and since then his behaviour has escalated. He attended creche from 9m, took 18m to settle and they said he was hypersensitive but didn't feel he had SEN. Since moving to school, we've had 2 meetings where they've flagged concerns about his behaviour, they've flip flopped between ASD and him being badly behaved, but I think they're back at ASD now as they are getting to know him. To me he seems to have ASD with a PDA profile. He will not do the simplest of tasks (getting dressed, brushing teeth, hand washing, leaving house) when asked & we use pda strategies which are effective. He's also very sensitive to noise, light, wind, etc. So possibly sensory issues. Obsessed with niche interests - latest being road signs and packaging signs, the list goes on. We have a psychologist appointment in June. After the 1st school meeting they suggested reduced hours & a packed lunch due to food issues. We agreed & asked for active feedback. We were under the impression things were improving but at the 2nd meeting they told us that there had been no change & they wanted 1 to 1 assistant paid by us, they suggested someone but she's unavailable. The main problem with DS is that when he hears no, you can't or has a demand placed on him, he will lash out, hair pulling, biting, hitting, throwing. If he spills water or food on himself he has a meltdown, throws food. This is not about a lack of boundaries we have been trying for 2 years, no change. I don't know what to do next - gut feeling is to pull him out of montessori & change setting because I think he's struggling with the big class, the activities (they have so many in the rooms I think it's overwhelming & they say he wants to play with them in a different way to the one intended), he just wants to play & it feels very serious, rules are confusing for him- "you can't run inside. But you can run outside but not with the toy wheelbarrow etc, or you can play with this but only in this way"
They don't have any SEN provision & say they've never experienced anything like him before. They are trying to accommodate & the last 2 weeks have been better, before they had 1 incident per day. I think hes struggling with the bilingual aspect too. He says he doesn't want to go, or like it but runs in - did the same at creche. I think a lot of his outbursts are anxiety related.

So my question, do I keep him there or move him? Compulsory school age is 4 so intake yr is 2025. He could go back to creche for one more year (15 kids per class) they know him and can accomodate. Or do I try a different setting like a traditional preschool. What should I be looking for? I strongly suspect he will be the same, he just needs time and understanding and not to be labelled naughty. We have 2 alternative options, 2 private schools 1 English school with a SEN department, 10 kids in a class & play based learning, lots of space & outside time, phased entry into school. I think he'd love it but it's a 30 min drive away. 2nd option is 15 min walk, some of his creche mates are there already, no SEN department. Less outside time but still play based, 15 kids in a class.
I did take him to trial English learning playgroup (3hr) last week that his friend goes to, 6 kids in a class, 2 teachers, he ran straight in. Lots of toys etc. They said they would be happy to take him but they had also found him defiant (didn't want to wash his hands that were covered in glue) and said he was quiet, played independently. But i did feel they treated him like the lovely little boy that he is and I worry the montessori have written him off as a bad kid.