Do all of the previously unallowed passive losses get deducted on line 8 of the 1040 when a rental property is disposed of? 

Yes

My understanding is that in the year of disposition, all passive losses and carryforwards are deducted.  I just want to make sure the passive losses can truly be included on line 8 to be used against all income not just against profit from the sale.

Yes.

I entered the disposition from the depreciation screen,  as a bulk sale and the sale is reported on 4797 part III with depreciation lowering the basis creating a small gain. 

Yes. 

In Lacerte, For a complete disposition, In Depreciation screen, enter a 1 in the Misc section under Sale of Asset to indicate complete disposition.  On F4797 EDPA will be added in front of the asset description.  EDPA = Entire Disposition of Passive Activity.

This year, there is no form 8582 but the entire unallowed passive losses from last year's 8582 and a current loss from this year are reported as a large loss on 1040 schedule 1 line 5 and 1040 line 8 and it is reducing the ordinary income by that large loss.

Yes. 

(and no - If you have another Passive Activity, F8582 is generated showing only the remaining Passive activity(ies)).