Is there a way to unseize an engine?

No matter how much you play with it the engine is still ruined. Do what Tom says.

Yes this works around 80 percent of the time you can pull all the plugs out and pour in oil where the spark plug goes until full let set un till oil seeps through the edges of the piston and rings add oil for a day or two some times it takes hours up to a couple days. This has worked for many old school mechanics and it also worked on my 2011 volvo c70. Not guranteed but is on the positive side to work. Good luck