Kristina did a great job with her response. I'd simply add that our ancestors weren't as fixed on a name's spelling as we are. Mark Twain’s autobiography gives us a sense of their views:
"I never had any large respect for good spelling. That is my feeling yet. Before the spelling-book came with its arbitrary forms, men unconsciously revealed shades of their characters and also added enlightening shades of expression to what they wrote by their spelling, and so it is possible that the spelling-book has been a doubtful benevolence to us."
If you haven't found variations of spellings for names, this probably means you haven't moved back very far along your tree.
Best wishes in your hunt!