I'd personally avoid adding oats to the cider. If you really want to do it anyways, I'd consider doing it to only half the batch, and doing it like a graff. It would require the use of some 2-row to actually convert the oats. A mash ratio of perhaps 3:1 oats to 2-row should work, but you'll probably want to use the BIAB technique, as a traditional sparge would definitely get stuck with anywhere near such a high proportion of oats.
Also, go easy on the spices. A little goes a loooong way, and it's easy to overdo it. You can always add more spice, but you can't take it out. Getting the spice level right also requires tasting it constantly, even if only a little bit. The longer the spices are steeped, the stronger their presence will be, so consider grinding the spices (freshly ground is ideal) and putting it in a very fine mesh bag, leaving the tie-off string at the top so that the bag can be removed when you find the spice level to be perfect. Spices that will work well include cinnamon, nutmeg, dry ginger, allspice, and cloves.
It's also very possible that you'll find that vanilla actually clashes with everything else (especially in more noticeable quantities), so wait until the end to add some vanilla extract, and make sure to test it on a small sample first! Once you find the ideal dosage, then you can scale it up to the full batch. If you really want to use actual vanilla bean, you'd be best off steeping the vanilla bean in a bit of vodka or other neutral grain alcohol for a few months, and then following the same process that was mentioned above for store-bought vanilla extract.
Good luck!