I bought Health Ins. through the Marketplace for 2018 & was given a PTC. My income raised year end I have to payback All of the PTC. Can I deduct the PTC amount as Prem?

Yes.  You can deduct your health insurance premiums and the repayment amount you paid.

The IRS states, any repayment of the Advance Premium Tax Credit is considered to be a premium payment in the same tax year.

Click this IRS link Publication 502, Medical and Dental Expenses (Including the Health Coverage Tax Credit) for more information.  Scroll down to Premium Tax Credit.