Without researching it, I agree that the At-Risk limits should not restrict the Self Employed Health Insurance deduction.

As for how to fill out the 6198, I'm not sure.  I don't have the program open to see the worksheet, but my thought is the health insurance should not be flowing to line 3.  But it is extremely rare that I need a 6198 (for me, when thing are limited, they are usually entirely limited by regular Basis, not At-Risk), so I am NOT fluent on it.