IconsGator.Com == some trademark issues here, otherwise an "ok" domain. My estimate is about 4 or 5 dollars. JMTemplates.com == I wouldn't consider it having anything to do with Joomla, but is a good brandable domain and I know my template sites are one of my more profitable types. On the other hand, there are a lot of combinations that you can grab. Without any work, I estimate a value of around 7 or 8 dollars, but you could easily do much better by throwing up a "template" site, lol.
possibly yes and possibly no. think hostgator.com. They could argue that almost anything related to website design was a trademark infringement. You might be okay as long as you make sure that none of the advertising or graphics looks anything like theirs and as long as you put a disclaimer somewhere that states that you have nothing to do with them. You would be surprised what can be a trademark infringement these days; I've had close to a hundred "complaints" over the years. Best wishes.