However, you can certainly get the funds to your Electrum wallet if you have the 3 private keys... One possible option would be to use a service like coinb.in to:
In fact he's already used coinb.in before you posted this tutorial, and somehow lost partial amount of his transaction.
I'm not sure why he still wants to import it to electrum because those keys already compromised (but coinb.in wasn't the culprit)
after initially accusing coinb.in, later he confirmed otherwise... here's the quote
---snip---EDIT May 23rd, 2018:After some further research, I discovered that someone else other than coinb.in may have had access to a private key.
I will update here once I compile some proof and reveal the identity of the scam artist. Sorry if my original post implied that coinb.in was the perp as it doesn't seem very likely anymore.
NOTES: You should consider the MultiSig Address (and the 3 private keys used) compromised if you do this... I would not recommend using that address or the private keys again.
as long as he is doing it all offline, except retrieving utxo and broadcasting signed raw transaction
I don't see why he should consider it (access to multisig) compromised, he created and owned all the three privkeys
but in this case, yes he shouldn't reuse it because it is confirmed compromised (his transaction was somehow altered)
although quite strange because he only lost partial amount, I'm curious to hear further development of his case
