Does damage from debris or asteroids cause stealth device to drop off

No, because they are not attacks.

No, because they are not attacks.

Only a direct attack that hits will remove a Stealth Device.

Damage from obstacles does not cause removal.

Neither does suffering damage or drawing cards due to bombs and/or the splash effect caused by certain other things.

If the mighty Wampa uses his pilot ability it may cause the ship to take a damage card BUT the actual attack is a miss so Stealth Device is not removed. Lt. Blount however will always "hits" with his attacks and will always remove a Stealth Device.

That's about it. Stealth device reads, "...if you are hit by an ATTACK...". As asteroid hits are not an attack, your stealth device is safe from the following:

1. Asteroids

2. Debris

3. Proximity Mines

4. Cluster Mines

5. Connor Nets

Also, to emphasize, you do not necessarily have to take damage to be hit by an attack. The aforementioned Lt. Blount, someone using draw their fire, tractor beams and so on are all attacks that can "hit", cause no damage to the target but still remove a stealth device.