3) BUT! If you say that you know publickey, we may use even faster solution, Kangaroo. I have prepared a special version of it to work with custom stride, somewhere on the forum I post explanation how it works. If it works, for 10 missing characters result will be done in VERY reasonable time.
If there is an outgoing transaction, then with the un/compressed public key and kangaroo or pollard, also possible.
Sadly this was an offline wallet, so it only ever had incoming transaction. It has never sent out.
@PawGo
New thread for that case
Missing 10 Characters in WIF Private Key - Can I recover them?
http://bitcointalk.org/index.php?topic=5379131.0