One more point - OP, have you spoken with your US bank to determine if it will accept $10K+ in foreign currency and, if so, what fees it will charge? All of this may be for naught. Some banks (branches) will not accept physical foreign cash or may accept it as your agent, pending on it processing (which can take a long time). This is both because the bank has no facility for doing anything with the currency other than shipping it and it has no capacity to determine whether the currency is forged.
To respond broadly:
1. Thanks to retired CBP inspector, but please recall that DHS & CBP have a very minor anti-money laundering role (AML). The issue here isn't whether the funds will be allowed into the country, it is what the fact of filing the form will do for OP going forward.
2. The question isn't whether OP pays some US taxes, it is the tax implications of repatriating (or perhaps patriating) funds earned overseas.
One poster above says three times he's not an expert, and that's the key. This is way too significant with risks attached to rely on anecodotal experiences fom the past.