More half mary advice

I'm heading into the last month of training for a July 26 half marathon. I wanted to train pretty aggressively for this race, but almost all of the half mary plans I found online were fairly low-mileage. So I took a marathon plan and made some adjustments, mostly shifting some miles from the ultra-long LSD runs to the mid-week runs, so I'd peak at 45 mpw with a 15-mile LSD. (This has the side benefit of setting me up nicely for high-mileage marathon training in the fall.)

I have a couple of questions. First, is it too late to start incorporating tempo runs into my training? The mary plan I was using called for a number of "marathon pace" runs, which I was going to make tempo runs, but a combination of factors kept me from doing most of those (I got the miles in, just not the pace/tempo part).

Second, what's the proper taper for a half marathon? The marathon plan would have me tapering for two or three weeks, but most half mary plans call for only a week or so. I'm still new enough to all this that I'm not sure what the best fit is for me. Right now my schedule for the last four weeks is:

42 miles (14m LSD)
45 miles (15m LSD)
45 miles (15m LSD)
19 miles (8m LSD -- this would be exactly one week before the race)
RACE

Thoughts? Advice?