Hi TopNan1 - I'm so sorry to hear that you are in this situation, & let us hope that it is only temporary. You have had some helpful responses & some not so helpful ones, but try to see the latter as more relevant to the posters own situation than yours, if you can.
At the same time tho, you must be desperate to do something, & you have been given an 'opening' by your son, the one accusation that you say you can own, so if it was me I would work with that one. I would write a letter or email genuinely apologising for that - as you say, "own it" though, don't try & justify it or belittle any reaction he had to it. Maybe that olive branch will be taken up & he will then apologise for other accusations which weren't true, who knows? But it's a starting point. None of us parents are perfect - I'm certainly not, & no argument is ever a 100% one way fault, & maybe just volunteering your own small part in it may help...
Just two small observations from me - any mention of "why should I?" , and calling yourself as "Top Nan" may not be perceived by others as a conciliatory mindset, so maybe try to make sure you keep an open mind if you do manage to start a conversation with him. Good luck!