Again, I think you've very confused about how MultiSig works and you're attempting to recover the wrong keys for what you're trying to achieve. All you need at this point is a wallet containing the "missing" MultiSig key, so you can sign transactions from your Linux wallet.

So, I'll try and breakdown what *my* understanding of the situation is:

- You have a MultiSig wallet on your Linux machine, that has coins in it, that you want to spend.

- LinuxWallet contains Linux private key + a public key from MacWallet as "co-signer"

- MacWallet is actually a 2FA wallet. It has x1 privateKey (stored in wallet file), x2 privateKey (normally "hidden", but accessible with seed) and x3 private key (held by TrustedCoin)

- Based on your description of the "co-signer" pubkeys in LinuxWallet, it would appear that the MacWallet pubkey it is using is the one that matches the "x1" private key from your 2FA MacWallet (NOTE: Without seeing the full pubkey, it is impossible to know if this is true, please double check the full pub key and make sure it is completely identical to the one reported in Linux wallet)

- if these assumptions are indeed correct, to be able to spend from your Linux wallet, you would need to extract the "x1" privkey from MacWallet (simply change the password, and leave the "new password" boxes empty, you can then open the wallet in a text editor to view the xprv)

- once you have the x1 xprv, create a "standard" wallet using just that xpriv. ("New/restore -> call it 'signingWallet' -> standard wallet -> use public or private keys", paste in the x1 xprv).

- you should now have the original LinuxWallet MultiSig and a new "standard" wallet on Mac that is using the x1 xprv.

- From here, you simply create a (partially signed) transaction on Linux, transfer it to the newly created 'signingWallet', sign it and then broadcast it.

- using LinuxWallet, create the transaction as desired (ie. Address, amount, fee etc). Click "sign" and put in wallet password (if any). You'll get the "preview" window pop up with options to Copy, Save, "send to cosigner" etc. Click "Save" and save the unsigned.txn file to USB.

- using 'signingWallet' on Mac goto: "Tools -> Load Transaction -> from file"... select the unsigned.txn file from the USB... you'll get the "preview" window open up. Verify it's all correct (fyi, it's normal for it to say "transaction unrelated to your wallet"), click sign, put in wallet password (if any) and then click broadcast.

Job done!

Personally, I'd recommend that once you have confirmed that the signing wallet is all working, that if you want to continue using a MultiSig setup, that you seriously consider creating a new pair of wallets, so you can easily recover using seeds... Rather than having to mess about with xprvs etc.