Re: Why can't the Federation use cloaking technology?
I'm not sure why the Romulans and Klingons get to use cloaking technology but the Federation doesn't. I mean, clearly there's a portion of a treaty somewhere (Treaty of Algeron, perhaps?) that says something to the effect that the Federation won't develop or use cloaking technology, thus Picard's aggrieved speech during TNG's "The Pegasus", but I don't know WHY the Federation would agree to such a unilateral limitation in the first place, especially when her at-the-time most intractable enemies use them willy-nilly. Such a "we can beat them fair and square without relying on being sneaky" approach seems rather naive from a real-world perspective. Like the Klingons say, "In war, there is nothing more honorable than victory"...
As you say it's down to the Treaty of Algeron, and once again as you say we don't know why, perhaps the Romulan's gave up something in the treaty that was equally valuable to the Federation.
On the continent of wild endeavour in the mountains of solace and solitude there stood the citadel of the time lords, the oldest and most mighty race in the universe looking down on the galaxies below sworn never to interfere only to watch.