Starting my minimal shoe/barefoot shoe

Hi thanks for all the great content! I've been working my way into this after having a lot of quad pain/spasms after finishing the LA marathon and noticing i was also destroying the outside heel of all my shoes in 250 or less miles. My typical shoe was the Brooks Ghost and Reeboks Floatride Energy. So far i've been walking / working everyday in xero shoes and have gotten up to 3-4 miles on run with minimal soreness except for a pulled right calf muscle and some right plantar fascitis on an extra fast and long run (1 minute faster than my typical marathon pace) and also noticing i'm beating up my heel on the downhills. Overall though, i've been loving how I feel walking and running with them, i tried a run or two in my old shoes and already its feeling weird and confining, like a lost a lot of sensory input of the surfaces! Questions:

1. Any tips for running downhill or running fast?
2. Do toe socks make a big difference? I ditched the Xero insole and prefer running barefoot in them , but its getting smelly! Looking at injinji toe socks but they are pricey! Maybe generic amazon toe socks?
3. Im running in Xero Zelens, is this an ideal shoe or any recommendations? Are toe shoes a big improvement? I am noticing my foot slides forward in them at times, especially wearing socks but no chafing yet. I'm amazed how comfortable they are!