Hi Howard,
You can read my blog we just recovered a blockchain like yours last week.
https://keychainx.medium.com/how-to-recover-blockchain-info-15-17-19-21-mnemonic-seed-8691cb59425
Your only way to get into the wallet is to "convince" someone at blockchain support to "reset" your confirmation mail.
They used to do this sometimes if you knew some other data like when then wallet was created, amount sent and/or IP used to login
It depends how you create the transaction.
Your IP when your broadcast a transaction through bitcoin core, is revealed to the other nodes that receives the broadcast. Which is approximately 10 other nodes.
ChainAnalysis a firm specializing in tracking bitcoin transactions used to have 10.000 BTC...