Mark, thanks for joining community! I'll tackle each of your questions separately. 

1) No, 1 signature claiming the Safe Harbor that the ENTERPRISE qualifies, not each property. Lacerte will generate the SH for signature. Scroll down here for instructions. https://accountants-community.intuit.com/articles/1797483&src=51247

2) Not necessarily. You are reading the guidance to aggregate separate QBI activities (like a Sch C, an S Corp, Rental, etc), and not necessarily rental properties. If you are using the SH for rentals, likely you are aggregating all the rentals as a single QBI activity. Only if you aggregate the Rental Activity with other QBI Activities, would you include an Aggregation schedule. However, if you are not treating all rentals as a single QBI Activity, then you may want to Aggregate for QBI purposes, and then remember that election is binding for future years. 

3) Yes, the Aggregation schedule must include the items you list. Lacerte includes them in the Aggregation worksheet.

Hope this helps.