I think the BSV from last year's transaction are lost & I don't want to lose any more. But, I don't really understand splitting and doubt I can avoid it happening again
That warning about no "
replay protection" is
just a minor issue if you're sending to your own wallet since you own the destination address, the fork coins are safe even if the same raw tx was broadcast to the other chain.
It's an issue with payments done using "
unsplit" addresses with output(s) that aren't in your control (
assuming that he can get the raw TX).
I think I did the transfer and sold around Nov 25th 2018. It was definitely after the forks.
You have transferred and sold in the same date?
If so, there will be no BSV coins in that wallet because
the transfer was done after the fork.
If so so, there might be BSV and BCH coins in your previous wallet (
the one you've used to send to blockchain.com) depending on the dates of the previous unspent and spent outputs.