Chrono Trigger DS couldn't just be testing the market, no one is stupid enough to try to sell a game three times and expect a break out hit each time. No matter how good it is.
4 times for the US and Japanese markets, less for PAL. And yes, products do that in video games quite a bit. How many times has Super Mario Bros (the well-known NES game) been rehashed and repacked? Enough times to be accessible on just about ever single console made by nintendo at least once.
Video games are all about money. Outside of the strange politics that has gotten involved in the Chrono Series, its the only driving force and statistic that matters to makers. Why hasn't there been another Chrono game to continue the story? "At E3 2009, SE Senior Vice President Shinji Hashimoto remarked, "If people want a sequel, they should buy more!"
What is is though is up to Square-Enix to figure out cause i sure as hell know that Cross didn't explain it well enough or in any great detail other than what we got.
They probably don't know either. That's part of why they can be scared of fan projects that try to interpret the series events for them.
Now the thing with guns and Rpg's, is just because its a 'gun' doesn't mean its as potent as the ones we use. One of lucca's early weapons was an air gun right? Based on how they develop their long range weapons, it's ammunition and projection force might do little to actually pierce armor, or break the skin. Heck, we don't even see archers in the olden eras of the game. As far as the Overthrow is concerned, they might have been using something more akin to a taser than a gun by our standards.
As far as Dalton's involvement goes, I wouldn't be surprised if he got some of the mystics to side with him. He is a potent caster, and mystics have disguised themselves before. Combine the numbers form Porre with the mystic continents, and a large force could effectively force a surrender.