Would lowHR training be beneficial for someone like me?

I made the most gains running easy runs fast. That entailed low 6:0x pace. My heart rate went from 180 to 155-160 when I got fit.

Sounds like you simply lack a mileage base. Follow the good old 80/20 rule. 80% of your runs in zone 2, 20% faster stuff. Build some aerobic capacity and those long runs will get much easier

This tells me that you really aren't aerobically developed at all, although your times are really good for most indicating good natural ability. In my experience, it took about 6 months to go from the slow slog to being able to run at a respectable pace in this heart zone. The important thing is to keep at it with good consistency

See the thing is, I've already done that but at the cost of multiple injuries. I ran my easy runs way faster than I should've to keep up with my teammates and to an extent it did help me but I was always burnt out and never really got "fit" for easy runs.

Were you never injured?

Yeah I'm aware I don't have to the best aerobic development.

My concern is, since I would do all my easy runs at a slow pace / low HR for some time, would I eventually lose fitness before gaining it again? I'm a pretty patient guy so 6 months is quite awesome (I live in the north east of USA) and it'll start warming up, etc.

This is true. My mileage in college would often be 25-30mi/wk. Most of it came from middle distance workouts.

My coach had me at 15mi/wk on the down weeks.

Also ran 5:50-6:10 pace and was never injured, but I'd sleep 9+ hours each night

I made a similar post as an 800m guy and some good discussions from V:

Work up to 40-45ish mpw and you'll see a huge difference

I still did workouts, base building stuff (lactate threshold repeats, progressions, etc) twice a week when I first started out.

I think the main take-home is that running in his lower zone every other day allows you to build mileage/volume without causing injury. It's a sort of positive feedback loop for fitness.

My other advice is to identify your zones using the HR reserve calculation (my garmin does the calculation automatically) - it gives you more wiggle room to run faster. The upper limit of my zone 2 is 159 bpm (154 / 204 (max) = 78% max HR). I feel this calculation reflects what is going on inside a lot better as I notice a clear difference in my breathing as I cross into zone 3 (>160). Whereas I feel the exact same whether I am running 60%, 65%, 75% except for the 60% feeling like torture and stupid at the same time.

You will notice that the day after workouts, your HR spikes higher at slower paces compared to when you are fully rested. This is normal and a good indicator that you need the easy miles that day

All this advice is just my own experience - you are faster than me at everything and I am not a coach. But I have taken large chunks off my distance PRs after sticking to this approach

You would definitely benefit from some easy mileage. You don't necessarily have to be a slave to the HR, but don't go running around in the 170s.

My recommendation would be to spend a couple of months getting up to 50-60 miles a week. Just take it comfortably easy on all the runs. Maybe do one fartlek a week or something. Keep an eye on the HR to see how it improves over time. But you will be fine running 8-something minute miles for a little while. That's plenty fast to feel like a real running stride, but slow enough to keep things easy.

Your shorter distance times are quite good. If you have goals at 5000 or above, you can make some serious gains by adding a lot of easy miles to your training.