With regard to tempo runs, one cannot stress enough that what matters on tempo runs is effort, not pace. 5:30 is a pretty fast tempo pace for someone of your current fitness, especially given the weather conditions you are currently dealing with. Yes, you need to be able to run 5:20 pace for 13.1 miles to meet your goal, but more importantly, you have to be able to run FAST AND RELAXED for 70 minutes.
To get to a point where you can run fast and relaxed for 70 minutes, you first have to be able to run fast and relaxed for 20-30 minutes. Trying to do tempo runs at a pace you're not currently ready for goes completely contrary to that goal. It's absolutely essential that you do your tempo runs at a manageable pace and let your growing fitness dictate what that pace is, rather than vice versa. Your next tempo run should probably be something like 30 minutes with no regard to pace. It will probably end up being something like 5:40-45. That's fine, even though it seems slow. Then maybe your next one will end up being 5:35-40 pace. And then after that, 5:30 pace. Etc.
Meanwhile, you also have to practice running at goal pace and slightly faster, in order to develop efficiency and confidence that that pace. You do that with intervals. Mostly long ones: my standby when I ran my PR of 69:10 was 6 x mile starting at about 5:10-15 pace, with 90 seconds rest (decreasing to 60 seconds rest as I got fitter over the course of a cycle). With these workouts you build your aerobic power and push your lactate threshold, but because you add the rest interval, you're able to stay relaxed while doing so. It's a different workout with a different purpose than the continuous tempo run, and you need to incorporate both.
Third, you need to do some work at faster than race pace in order to improve efficiency and make race pace more manageable. Things like VO2 max intervals - you already have this in your history with the 1K repeats.
Fourth, your long runs need to be productive. You have to use them to work on running hard while you're tired. Easy long runs are only good for preparing you for hard long runs. So alternate them, an easy LR with a hard one that includes something like 2M intervals at about marathon pace, a fast finish, and occasionally a long run done entirely at a FAST pace - for you, likely something like 14M starting around 6:10-20 and working down under 6 by the end.
Incorporating all of these elements will get you there. But you have to let the fitness come to you, and not force it. Doing your tempo runs at a set pace, instead of letting the pace increase gradually with your fitness, is forcing it.
Here's a sample four week block from my log. This was from 10 to 6 weeks out from my HM PR.
Monday - 6M tempo run. Average pace 5:42.
Tuesday - Easy double 8/5
Wednesday - easy double 10/5, strides
Thursday - 12 x 1 min on, 1 min off at 5k effort
Friday - easy run 10 miles
Saturday - easy double 9/6
Sunday - 18M easy long run, average pace 6:39
Monday - easy run 8 miles
Tuesday - easy double 10/5, strides
Wednesday - 6 x mile with 90 seconds rest, average 5:17
Thursday - easy double 9/5
Friday - easy double 10/6
Saturday - long run 16M including 3 x 2 miles at 5:51, 5:44, 5:39
Sunday - easy run 7 miles
Monday - easy double 10/5
Tuesday - 10x800 average 2:26
Wednesday - easy run 8 miles
Thursday - 6 mile tempo average pace 5:34
Friday - easy double 8/6
Saturday - easy run 10 miles
Sunday - easy long run 20 miles, average pace 6:43
Monday - easy run 6 miles
Tuesday - easy double 10/7
Wednesday - 6 x mile with 60 seconds rest, average 5:16
Thursday - easy double 8/7
Friday - easy run 10 miles
Saturday - long run w/ fast finish (18M with first 14 easy, last 4 progressing from 5:45 to 5:33)
Sunday - easy double 5/5