OK: 36 tooth (front) ÷ 14 tooth (mid hub input) x 22 tooth (output) ÷ 18 tooth (cog) x 24" (-ish) diameter wheel yields these gear inch numbers:

1st: 47.0
2nd: 56.5
3rd: 75.3
4th: 100.3
5th: 120.4

As you've found, these are very, very high gears, suitable for a running a streamliner at Bonneville but not much else. A typical trike would have a low gear around 30 gear inches and a high of 80 gear inches. To do this I would change the cog on the SRF5(W) hub to something much larger, around 22 teeth. That gives you this:
36 tooth (front) ÷ 22 tooth (mid hub input) x 22 tooth (output) ÷ 18 tooth (cog) x 24" diameter wheel yielding these gear inch numbers:

1st: 29.9
2nd: 35.9
3rd: 47.9
4th: 63.9
5th: 76.6

In order to get the chain to work you'll probably have to add a couple links to it or replace it entirely. "Cutting" a bike chain to length is pretty easy- there's probably thousands of YouTube videos on how to do it.

This should suit you unless you're climbing steep hills. If you're climbing hills and you're a "big boy", you should look into a trike with more gears, like a 24 or 27 speed.

You're asking the right questions... keep going!