OK, so I think you have bigger problems than the laptop, which is what I suspected.
The school absolutely can and must make reasonable adjustments to the behaviour policy.
1 and 2 should not be an issue either.
Depending on the class, 3 may be a problem, depending on the class. There may be other DC with SEN who need to sit front and centre. Some of those may have EHCPs which mandate it. That isn’t to say the school should shrug their shoulders and do nothing, though.
Rather than just looking at placement within the classroom, I would have also expected the OT to make other recommendations around copying from the board. For example, minimising copying and ensuring DS is provided with handouts/power-points, etc. The use of assistive tech on the laptop (or a tablet, which some find more helpful because they can take a photograph, then annotate) to help with recording work.
If you aren’t getting anywhere with the SENCO, I would escalate it higher up the chain. Request a meeting with whatever member of the senior leadership team has responsibility for SEN.
If you have the email addresses of DS’s teachers, I would email them directly.
Does DS have an SEN plan, e.g. IEP, one page profile, MyPlan. Called different things in different schools/areas but will set out the support DS needs.
For forgetting equipment, we find it helps DS2 to have two sets. One set remains at home. The other set is never taken out of his bag at home. Now items are lost at school, but it means his e.g. calculator is never left at home because he forgot to put it back in his bag.