Drivetrain

I currently have a Pocket Rocket with an 11- to 28-tooth cog set, a SRAM 3x8 hub and a 48-tooth chainring. In reading the specs for the new Pocket Rocket vs. the New World Tourist, I noticed that the NWT has a lower gear range than the PR. Both have a 46-tooth chainring and 11- to 28-tooth cog set. I am confused on the math.

I would like the lower gears of the NWT for my PR. Is that possible? Is changing the chainring the best solution? Is there any way to get the 22.5-107 that NWT has?

I'm trying to calculate the gear-inches for my Pocket Rocket (451mm wheels). It has the SRAM 3x7 hub. Can you tell me:
1. What is the size of the wheel in inches?
2. What are the multipliers involved with the 3x7 hub?

My New World Tourist can be adjusted to shift well either at the high end (small sprockets) or the low end (large sprockets). I haven't been able to find a compromise that has it shifting smoothly throughout the range. It has twist grip shifters. Any suggestions?

My wife and I own are planning a multi-month tour of Europe, plenty of mountains. We would like to lower our gearing. We currently have the Sachs 3-speed hub with 44 x 11-30. Our convential touring bikes, Co-Motion customs, give us granny gears with 17.88 and 18.56 gear inches.

Any suggestions on lowering our Llama gearing to be closer to our Co-motion gearing?