1)Envoys are fine as a class. In terms of applying violence to enemies, you won't be doing too much of that in combat (although by and large you'll have a single swing so generally an unwieldy weapon will serve you best).
2) It's not ideal, but it's manageable. You'll have less resolve, but having non-max charisma shouldn't be a deal breaker. Many of the best improvs don't feature a save so it's not critical although you'll still do well to keep it high
3)Skills are up to you. You get a metric boatload but perception and face skills are basically "expected" of the class. I'd also recommend any or all of piloting, engineering, or computers to give you something to do in space combat other than Captain. As for trap options...Can't really tell you. Obviously early on you should avoid stuff with a save till you can ratchet up your Cha, but there's plenty of options till then. (Improved) Get Em is basically required, Expanded Attunement is handy if you want to cover your bases with other android party members or future proofing for Eox characters. The rest are up to you really. There's very few options that will trick you into taking them. Just remember, under nearly all circumstances you're only ever going to swing once in combat, something has gone horribly wrong if you're full attacking.
4)If you want to murder things more often sure. Envoys are a pretty hard support class which is a turn off for many people. If spending half your turns marking targets, shouting encouragement/similar and maybe taking a single potshot is unappealing then a soldier or solarian icon may be more your style. Just watch out for the drop in skill points and scaling bonuses to them.
