Certified GKH Gardening Expert
Many times the seeds can be harvested by gently shaking the cone once it's dried and from the tree. Or you can open the pine scales and then shake them out. Yes, you can put 2-3 seeds per pot and just thin out as needed, usually keeping the strongest.
If you haven't already read it, this article can help: https://www.gardeningknowhow.com/ornamental/trees/pine/how-to-grow-a-pine-tree-from-seed.htm