Is there anything going on in the parks or elsewhere on friday may 10 that would affect not being able to get a single reservation anywhere for that day?
And as a note, if you're doing the 180+10, the +10 is inclusive, so you would only be able to book 4/30 - 5/09.
For example, if you were checking in today (this is illustrated best by the first of the month ), you could have booked 180 days ago for today (11/01) through 11/10 and not 11/11.