If you have a single entry visa and want to maintain it then yes you would need a re-entry permit. If you (just possible), have a multi-entry visa then you would not need a re-entry permit.
ask your wife to delay by 2 months the divorce, get your normal marriage extension, then divorce in 2 months, take your divorce and your bank stuff to immigration to change the reason of extension to retirement.
you can apply up to 30 days early if that helps? no you do not need to cancel your current extension, yes you can come back on visa exempt, apply for a non-o and then subsequent extension.