How to fix toilet spacing doesn't meet minimum 15"?
It reads like you have already answered your own question: either get rid of the vanity or move the toilet flange over, if you need to abide by a toilet side clearance code. 

Google "offset toilet flange" for hundreds of hits, including Amazon and the big box stores.

It may be easier and better drainage to just place a new (straight) flange where you want it. A jack hammer would be overkill. A 1/2" hammer-drill will do on the concrete basement floor.