"The 8606 instructions clearly say to enter the line 15b on the 1040 line 4b and the 8915-E say to enter line 19 on the 1040 line 4b. "
even though it says "enter" not "include", when two forms reference the same line, you have to combine the amounts.
If you reduce the amount paid back to $30,000 there is a taxable COVID amount and a taxable unqualified amount from form 8606 line 15c (which does use the word "include"), not 15b, and the sum should be on 1040 line 4b.
