Well, fair enough. But. I don't think there's a reason to believe Mueller didn't lay any perjury traps. He's done it with everyone. It's just that he didn't need it with Stone and some others, because they were perfectly willing to lie. Probably it would be helpful to have an attorney present during questioning who can help them traverse the questions and hint at what they don't have to lie about.
hahaha
Absolutely! I think some of Trump's unforced errors (and those around him) are because they are new to this. Well, Stone and Manafort weren't, but they have other issues.
In terms of perjury traps, that's something the FBI does regularly. That isn't unique to Trump or the Mueller investigation. Heck, arguably, Clinton (Bill) got caught by one, and it wasn't even set by federal law enforcement.