When I used to work in this field (a long time ago now), PE was regularly threatened and carried out when children had behavioural difficulties in primary schools. These days, schools are supposed to be more inclusive but some do throw the towel in. They cite exactly what yours has done. They cannot meet the needs of your child and they think other children are not safe.
I would also think the LA and the SEND Officers will have great difficulty in persuading another mainstream school to have him. They can alter the statement to the "best fit" mainstream school but if they cannot establish a good relationship with this school, then you are not in a good position for success. For example, a school may already have 30 in the class. They may already have quite a few SEND children. Even mainstream schools that have fantastic experience of behaviour difficulties will find an additional child with complex behavioural needs very difficult to cope with and may not welcome the challenge.
If I was doing my old job now - I would be talking to the Statement team and the Ed Psychs as a matter of urgency to see if they thought mainstream was realistic for the immediate future, or whether we should look at an appropriate Special School.
I am not sure a disciplined approach in a mainstream school is really possible. It would take a huge amount of effort and would be quite a different approach to that employed in many mainstream schools.
Special Schools have staff who are experienced and qualified to deal with his behaviour on a daily basis. Much more individual attention because of significantly higher staff/pupil ratios and usually a very calm and purposeful ethos with clear rules and consequences, but understanding at the same time. I would try and see what his Ed Psych thinks as they have experience of similar children and are an important cog in the statement process. I have no doubt your existing (previous) Head will be making it clear they are unable to educate him in mainstream. Therefore I really would try to get expert teaching, smaller classes and a school that wants him. No child has to stay at a special school if they improve. They can reintegrate. Spaces at Special Schools are at a premium but if the LA cannot find a mainstream school, they will negotiate with the Head of the Special School as they will need to offer him a place at an appropriate school. Hope your meeting goes well.