Most bang for my buck in 55 days (Half Marathon training)?

Look for pro help. Look for JS.

I remember your earlier thread. Sorry to hear the first race didn't go as well as you hoped.

For an 8-week HM buildup, I'd say the biggest payoff comes from

1. Increased weekly mileage (and your plan for 100-115 km/w sounds about perfect)

2. Long intervals (work up to 3 x 3km, and past that if possible; 4 x 3km or 3 x 4m would be great, but 3 x 5km was excessive when I tried it)

Since you're increasing mileage, your long run will probably get a bit longer as well, but eventually getting somewhere in the neighborhood of 27-28km is sufficient. If you haven't done many long tempos, you might gain a lot from something like 15km at what feels like MP.

How much did you taper for your race? I find I benefit from having the peak workout 10+ days out and then reducing mileage sharply, but everyone handles things a bit different.

How familiar are you with the course for your upcoming race? Knowing what the start is like and how the course goes can be a huge benefit. Running wide on turns and not following tangents can easily add 2:00 to a HM.

I think 80-100 k per week including two workouts is enough. Each workout should be purely threshold based, 2x5, 3x3 or fartlek with a total of 15 k. Don't overdo them as you want to be able to run also the following day. Eat enough, especially in workout days. Don't go crazy on easy days.