Looks like you have a great top to work with!!
Your batting does not need to be larger than your lining, I usually cut my the same size as my top, but with this being your first, you can decide that.
First of all, if you are hand quilting, you need to baste the layers, either with a long stitch, safety pins or spray adhesive,if you are using that type of hoop you have pictured rather than in a large frame. For that hoop, you are right to start in the center, but your hoop is a little small. It's ok to go back and quilt hearts once you finished. You can either quilt in the ditch or you can quilt on each side of the seams. Either way, you don't need to mark those lines on there. Keep the lines straight by watching where the needle lays against the fabric when you are rocking it through the layers to pick up more fabric. The seam is the guide. If you've never quilting before, you might want to start with a sz 9 needle.
Hope this helps.... Happy quilting. Got to go work on mine!