H1B approved but security check going

I am on F1 (still have 1 year of OPT-extension), applied for H1B visa 2018. Replied for RFE and was waiting for the result.
I am traveling to my home country for my marriage and can’t postpone it.
Applied for Travel I20 as a secondary option and got to know that my SEVIS was completed as my H1B got approved. While there is no update in the USCIS online portal and no approval notice has been received.
Employer reached USCIS and got to know that my H1B got approved on Nov 19th, 2018 and valid till Aug 2021. They said that H1B was not completely approved as background clearance is going on and they will mail us approval notice once security clearance is completed and got to know that it may take months in some cases.

As I need to travel in 10 days, what options do I have to come back safely?
Please let me know if you know any other option.

You may reach out to your congressman/congresswoman or senator or governor, explain your situation and request them to write a letter to expedite the process as you have to go for your marriage. It might work. Few people got such results.