Seventeen pages an eight worksheets in the 68-page IRS Pub 974 are dedicated to this issue. This issue will never apply to me personally, so it just ended up being that I don't have the time to understand it thoroughly enough to continue trying to answer questions about it.
Still, with regard to the amount of APTC that you don't have to pay back due to the repayment limitation, I don't know that that needs to be taken into account when figuring your SEHID.
