Your central question was whether you could use Ilford filters with Agfa papers, and you got the right answer several times - yes.
But a point that may not have been stated clearly is that the response of Agfa papers to Ilford filters will be slightly different than the result of those papers to Kodak filters, or DuPont filters (if you can find them). Those differences are not important as long as you don't intermix filters. In other words, if you stick with your Ilford filters, all you really need to know is that the grade 1 filter will result in a softer print than the grade 2 filter, while the grade 3 filter will give higher contrast results than #2, etc. And as you work with them over time, you will develop a sense of how the paper responds, and will be able to more quickly home in on the filter that gives you the result that you are seeking for a given negative. But if you try mixing Ilford and Kodak filters, you will find that the results you get will necessarily follow a consistent pattern, and that will be very frustrating.