First point: not in my game. They've been reduced to not-influential in my game. They have no tech, they have no space stations, they have the second smallest fleet (trumped only by the Burlusts, who are under orbital bombardment by 700 ships, so anything they build get blown up in 0.2 seconds of relative time).
Second point: I did not find the virus that exploitable. I've had it run out of ammo, it also doesn't have the 100% effectiveness that it implies.
Third and Fourth points: haven't used it.
Fifth: Didn't care about them, the Skylaxians very rapidly decided that the Burlusts had to die-die-die so I just let them.
Sixth: Tech progression is odd. I kind of wish that different races would research different things, but it seems that everyone has the same priorities...but different research rates. It also bugs me that every tech that is beneficial to me is exactly the same: 20% more shields, 10% more armor (oh and the AI gets 20% more damage).
Seventh: Can't comment. I did one such mission and it was my own fault (attacked the planet on my own, there were 78(!) flagships, no surprise I got killed).
Eighth: See six.
On Ten: I wish it was harder. Right now it (seems!) like if you can get a race into the Federation they stick around, no qualms. Oh and you can get them into the Federation, if it exists, without meeting the "form a federation" requirements! I did a lot of work to get 3 races that liked each other only to find that once I'd formed the Federation all I had to do was go to the Peltians and say "hey guys, want in? Here's 150 worthless voting proxies" and they go "sure!" and jump right in. There wasn't even a "Eeeh...we're not so sure about those Thoraxians (Relationship is only 78)" complaint. This really bugged me later when I got the Skylaxians in: they still had only a neutral opinion of the Peltians (12)! It'll even let me get the Boarines onboard (according to the Federation Progress screen), even though they hate the Thoraxians (-30ish?), if only I could find the freaking option in their race dialogs.