Pruning a damaged apple tree

I'm looking for suggestions as to how to prune this apple tree. It had multiple cultivars grafted on it originally but now has only 2 cultivars left. Without a central leader I'm worried that a big storm will split it.  I would like to try to keep both cultivars but am not sure where to start.

I think you have good reason to be concerned. There is a lot of weight out away from vertical, and already looks like there is a split partially formed in the short section of trunk.

If it were my tree I would consider a drastic reduction to bring the weight more central. The two remaining upright would become new central-ish leaders, to establish a new framework from.

My experience is that apples benefit from pruning to ensure they get a really robust framework. The trees I have had fail have all be ones that were left to grow without pruning and ended up breaking under the weight of fruit. Cutting back also seems to give fewer but bigger fruit, in my fairly limited experience.

I like what Michael has suggested, maybe cutting back even harder. What I would do too is get some seedlings of some local apple trees, even crabapples, but on their own root (if you haven't got some already growing. Keep some of the younger wood from the tree as you prune it and have a go at grafting. Hopefully you will be able to make new trees of each of the varieties, just in case the main tree doesn't like the surgery. Hopefully it will recover and be better in the long run.
Here's one thread on grafting: https://permies.com/t/44458/Grafting-Trees. It's probably a bit early to actually graft now (but a good time to prune while dormant perhaps) so you could stick the scionwood in the ground temporarily, or in the 'fridge (somewhere cool).
You might have enough apple wood from those branches to make something cool too. Even a wooden spoon would be a nice thing: https://permies.com/wiki/126961/pep-woodworking/PEP-BB-roundwood-straw-lightspoon