It does seem a little strange to exercise an option when the FMV is less than the strike price.
In almost all cases there's absolutely no real "income tax return reporting" reason to use the ISO step by step interview.
Your basis per share is $1.50 and I'd assume there's no effect of the ISO exercise on your W-2. So simply use the default 1099-B entry form and report the sale that way. Normally, entering the sale of stock acquired via an ISO using the default 1099-B entry form requires that you adjust the basis reported on the 1099-B, but I'd guess that wouldn't be necessary in this case as I'd think the broker did use that $1.50 per share.
