Thank you everyone,
Mr Limpet is doing great now. He is settling in and I am trying everything everyone suggested from links and your own advice. He's even built a nice sized bubble nest :).
I have been looking at live plant options for the tank and also would like to purchase a better water heater today. His temperatures have been a stable 76 so it's at the lower end of optimal I think. I imagine he will be happier once the water is a little warmer and more consistently so. All of the water changes have been "practice" for us so he might still be a little stressed but we are learning and he is more active. He loves his space and I am doing my best to provide more to make him most comfortable in our home.
I am acclimating him to his food currently, considering he will eat if he is hungry and giving him time. I'm stretching this mornings meal maybe for another hour or two.
He has had two water changes in two days since his move into the bigger tank.
The first time we changed the water in his 5g tank, it got every dirty quickly so I decided it was best to perform another change and did the best I could to measure precisely and increasing his water to 3 gallons. We do not have a top for the tank so I am being cautious but once I buy it I will increase the water amount by another gallon up to 4.
If you have read this far,
My only other question would be towards lighting, will he be okay with a black light? Or other kinds of "colored" lighting?