There is no movement in the prison system at the moment due to COVID 19 but in usual times he would go in as Cat A but they would then be seeking to down categorize him as soon as possible.
This doesn't mean he isn't a high risk offender - it means he isn't dangerous to other inmates and prison staff - Cat A is usually terrorists, gang offenders, people who are violent within prison.
So you can be very high risk to the public and still be Cat C if you see what I mean. Most people like him would be in a Cat C specialist prison.
He would be held as a VP and have no contact with anyone else who wasn't a VP - there are many many sex offenders unfortunately to the extent there are whole prisons just for sex offenders so he will not be living in fear of being attacked.
Healthcare for prisoners also has to be equal to that of non-prisoners - you do get treated for cancer if you are a prisoner, regardless of what you are in prison for although it can be challenging to do it.
However and I hope this reassures the OP - he is 72 and has a 16 year sentence. Even if he got parole first time he would be 80 - it is very rare, especially given the nature of his offending and that he was offending right up to conviction, for people to get parole first time. So add some years on to that, he'll be older than 80.
Plus now he has been convicted, with the publicity these men do have additional cases brought against them while they are in prison. So he may get extra years. Add a few years on for that.
Even if he did get released, he'd be a very very old man - say 85, living far away from you, under tight parole conditions. Recalls back to prison are very common. So he may end up back in prison.
What he has is effectively a life sentence. Well done OP. You are indeed a Warrior Woman.