Incorrect PRs for RM where FG made at external ven...

My first ever question on this portal, apologies if the terms are too generic/incorrect.

Scenario/Set-up : I have my company target DC location "X" and an external vendor. My RM are delivered by suppliers to "X" and all of it is then posted to vendor using 541 movement at "X" and 101 movement at vendor. So, the stock on hand basically sits at vendor location. I place my POs for FG/maintain BOM/routing against "X" in ECC. 

The dep demand on the RM is calculated in APO at vendor level which appears as dist demand for "X". I was trying to make system to calculate/suggest me the PRs for these RM, but it doesn't make sense and I have below issues:

1. Timing - PR at target "X" is suggesting a delivery date where there is no requirement of an order[much advance than needed]. currently, Safety days supply maintained at vendor location with SZ method. 

2. Quantity : Overall qty seems to be okay, but they are coming up as multiple PRs with same date or 1 week apart[again no new production in the next 1 week window], I have min lot size and rounding value maintained at target "X" and nothing on Max lot size. 

3. Product Heuristic in APO is SAP_PP_002 at vendor location.

Please could anyone guide me thru this issue.