If you would like to comfortably run for example 6.15 for say one or two minutes, then you need to train yourself such that 6.15 is not close to your top speed. To do that, you need to repeatedly run significantly faster than that. For example try 8 times 30 or 60 seconds at 6.00 (or faster if you can) with a minute of rest between. Make sure you are warmed up, and perhaps take it a bit easier on the first two reps.
My impression is that New Balance has moved to more narrow models. I just bought a new pair of hooka Cliftons. They are not cheap and far from minimal, but they come in regular and wide models. For more minimal and whide I like Altra torin and Altra escalante. Wide shoes are still niche - I don’t know any lower price options.