Correct MAGolding!
Largely the clues speak for themselves.
Regarding clues 1 and 4, it's quite interesting to speculate how Garth got the materials to create the bomb, and then add it to the facility's systems.
Twice he talks of his 'latest invention'. To an extent, it's probably easy to manipulate the chair, but I find it hard to believe any dangerous chemicals would be on a facility such as this. Maybe the raw elements were on the surface, or perhaps Garth tricked another vessel beforehand to gain the materials? Perhaps he destroyed the vessel when the crew would not co-operate?
(As an aside, if he can change appearances, I find it hard to believe he didn't escape before now.)
Anyhow, over to you sir!