Argo uses his conventional weaponry before resorting to the Nucleo-protonic blasts because, as we learn immediately after this, those blasts are powered directly from his core and rapidly drain his fuel supply. He probably expends drastically less energy powering his conventional weapons even though they are weaker than his plasma blasts. This is probably why he doesn't open with them and uses them as an absolute last resort.
They only ever made one Big Guy because while the suit turns any single person into a one-man army, it's shown that the logistics of keeping Big Guy supplied and ready is staggering; a whole crew of an Aircraft Carrier is kept at the ready 24/7 to rearm and ready The Big Guy for when he's needed. While his effectiveness is unquestionable, it's likely to be much more economical to just send in conventional troops (as they do in some episodes), especially since it's implied that the pit crew that directly handle his maintenance are not just normal mechanics, but scientists in their own right (which would make them exceedingly hard to train enmasse).
Jenny, Dr. Donovan's talking monkey has been shown to have a husband/wife relationship with him in "Lowest Depths." Furthermore, in episode 3, she mentioned having relatives in Borneo. That's all we really know about her. This brings up some rather unpleasant implications. Was Jenny once human? Did some kind of weird tech turn Axel Donovan's wife into a monkey? Did Donovan somehow "uplift" an ordinary monkey? and enter some kind of marriage pact? What was Donovan doing in Borneo?
