1) What you can do, is send two ships. One sat layer, and one cargo ship. Transfer sats one by one to the layer, and lay them singly.
2) Nebulae Range from cloaking level 1 to 5. If you're deploying in a nebula, the stealth armor will be worthless, since the nebula does that for you
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Red, and cyan(IIRC) are levels 5 and 4, and there is no unmodded sensor to pierce that. Mines are your only alternative.
In the other 3 color nebulae, a level 3 sensor will do fine.