I've come up against this forum 'limitation' recently myself when I went to 'preview'/'save' something I'm currently drafting up.
I ended up having to delete some of the sentences in my lengthy draft until it went below the maximum 64000 characters limitation, and then saved that....before just continuing to draft up a second post to incorporate what I'd deleted in the first one.
When I'm ready, I'll just have to post one after the other, it seems.
Unless Jay suggests otherwise, you may have to do the same Frink.