Not sure why your images don't work, so I posted them again.
I'd consider that trashed. You may find someone who can weld in a new patch of alu or replace the seat tube completely (which is the better option), but the big question is if it's worth the cost and effort.
There are dual seatpost clamps, where one part clamps the frame and another part clamps the seatpost itself.
Example : Ebay link
That might help with the spinning, but I wouldn't hold my breath and even if it works I still wouldn't trust it for any serious riding anymore.
When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
You could insert a correctly sized steel seatpost to the correct height. Leave in a damp place & water regularly with salt water for a few weeks. It will probably never move again. Sanding any protective finish off the seatpost which sits in the frame & cleaning any grease or oil from inside the seat tube will accelerate the bimetallic corrosion. If you tidy up the broken edges first then the seat clamp will cover the damage.
Scores 8.7 in the Bodge it & scarper world cup but will keep it rolling :facepalm: .