Mulch: Don't use the recycled rubber mulch in a home garden - in addition to what was already said, it will do absolutely nothing for the soil and will get hotter than wood mulch. Don't worry too much about wood mulch tying up or drawing nitrogen from the soil, just use finer mulch and not the larger hardwood chips, and no more than 3" deep. Natural cedar or hemlock mulch is best.
Nematodes: reapply in late summer - so August or September. Different grubs turn into different insects, and so they have different life cycles. Many feed in both the spring and late summer, but some also primarily feed on the summer and less in the spring. A spring and a fall application will keep most grub populations under control.
Anyone here can PM me your email address if you want a document I put together for lawn pests and control.