If a small ship has an asteroid and something else, like CR90 or GR75 in the way, does it get multiple obstacle bonus defense dice?

No.

An attack is Obstructed if it has 1 or more obstacles between it and the target. An obstructed attack gives the defender +1 evade dice.

There are however some cards that can change the number of dice like the one with the GR-75.

The GR-75 comes with the deflector sheilds upgrade card that bumps the number of dice from 1 to 3 for an obstructed shot, but you have to have it equipped.

The GR-75 comes with the deflector sheilds upgrade card that bumps the number of dice from 1 to 3 for an obstructed shot, but you have to have it equipped.

It's the EM Emitter. Also important to note that this doesn't change the yes/no nature of obstructed shots, only the number of dice rolled if the huge ship is part of the obstruction. So:

Is the shot obstructed?

--- No: No extra dice

--- Yes, then is the shot obstructed by a huge ship with an EM Emitter?

------ No: +1 defense die

------ Yes: +3 defense dice

Got it. Thanks everyone.