So this is exactly it. Regarding Point #2, I see that the address shown that the larger transaction is going to is in my "address" tab on elecrum, as a previous receiving address. Does this indicate that I am able to approve the message?
I won't say what you should do, I would be uneasy too with such messages (and I don't know how good you checked the addresses, no offense).
I've sent you quite a long message in private, I don't know how your tx looks like, I will post it here too:
It depends also how you do it.
If you have value_x on Your_Address_1 and just want to send value_y to Coinbase_Address_1, your transaction will be
In: Your_Address_1
Out_1: Coinbase_Address_1
Out_2: Your_Address_2 (the change, meaning value_x - (value_y + tx fee))
Now, if you have made yourself the transaction as "Pay to many" and put yourself Your_Address_2 you wanted, this may be the problem; in my case this was it and I've fixed it by NOT using Pay to Many and instead only send to Coinbase_Address_1 and let the wallet do the rest.
Problem 1: I don't know what you actually done and you don't look as somebody that would have been using pay to many.
Problem 2: This kind of things should be discussed publicly because I may be a scammer trying to get more info from you and steal your money. And it should be public because others may also have good ideas.
Problem 3: I don't know if your Electrum is clean. I don't want to scare you, but another direction would be to uninstall Electrum, download it, verify the signature and install/run it again; just to make sure you don't have some odd Electrum clone that's trying something fishy. --> update, this may not be the case if the second address is indeed part of your wallet
Since my use case differs from yours, since I didn't do multisig (and I don't have experience with that), I'll leave to the others find a way that maybe the Ledger won't complain. I think that such direction would still be option #1.
