Honestly, I don't think I would worry too much about the difference in spelling. Scotland's People transcribers are pretty meticulous, so that's probably a best guess on their transcription in the index. Then you have a separate group indexing for Family Search and they too used the Finwick spelling. At least it's his middle name, not his surname! Record it as Finwick in the data fields, and then note in his bio that the spelling changed over his lifetime.