Yeah, there is a lot to learn! I don't know much myself! But if I keep working at it....

One puzzle: the cassette fits to the hub, not the rim. To get more spokes, you must have gotten a new hub also. Mostly new hubs are "free hubs" rather than the old freewheels. But maybe the Revel 2 came with a freewheel hub set-up. That would explain the incompatibility.

One idea I have: the new cassette might not be exactly in the same relationship to the rear derailleur as the old cassette. You might have to adjust both the cable slack and also tweak the adjusting screws, to let the derailleur go out a bit further. Perhaps it can't shift completely to that smallest cog. A bit of adjustment of the rear derailleur when switching the whole rear hub set-up, that seems like a first try-this.

Yeah you might need to take a link out of your chain because the cog is smaller. Actually you should really replace the chain. The old chain will have stretched to match the wear on the old cassette. Though if you only had a few hundred miles on the old set-up it is probably no big deal. But a new cassette can easily require a new chain.