If i understood your problem correctly, you are trying to fetch all product numbers from the list and populating it in a drop down in infopath form.
If there are more than 5000 items in the list and you are trying to retrieve all of them at once, then it will be a problem as SharePoint has a limitation of threshold value which is by default set to 5000 items. You can change this value but then there will be a lock on the table in SQL Server and no other operation can be performed at that time.
I think populating all of the items at once is not the best idea here. I would suggest you here to create few more dropdowns in infopath forms and categories your data. Rather than loading all items in one dropdown, first load main categories in first dropdown and than its sub categories in second dropdown and then load the product numbers in third dropdown which you have currently.
You have to do something on your data organization level if its really the threshold issue. Or change the way you are retrieving data in InfoPath form by categorizing it.
Hope that makes sense.