1. I'd have a hard time seeing that small screen onstage, and my big foot would likely mash the wrong effects button. Others might find it easier.
2. There are tons of good, cheap effects boxes out there, and easy to find used. I like Pi boxes, but this seems like a homebrew replication of what's on the market.
3. All good boxes are low-latency, in my experience. It's a fundamental thing I think most players need.