How confirm my own doublespend transaction got confirmed
The answer is actually that you will receive a negative confirmation count in this case. (The bitcoin documentation is just terrible..)

See the bitcoin core release notes of 0.12.0 - section "Wallet: Negative confirmations and conflict detection"

https://bitcoin.org/en/release/v0.12.0

update note: In case of a negative confirmation (conflict detected) be sure to fetch all parent tx of that tx and see if that one got confirmed