Hmmm. Okay. I'm far from being an expert on this, so hopefully someone more knowledgable than me will jump in and help (and correct any bad advice I may give). Lets see how we can break this down...
<b>The current 135:</b>
It sounds like you overwhelmed your biofilter with the addition of LR before it was fully cured. Some questions about the setup as it stands right now:
1) Is that testing okay for ammonia because you added prime to the 135, or because the LR is not in there and the biofilter took care of it? If you are adding prime to keep the amonia and nitrite down, you will need to take out the remaining livestock and probably toss in the LR and let the 135 completely cycle before you _slowly_ start to reintroduce the livestock. If the current biofilter was okay with all of those fish, then you likely can stop adding prime and see what the params do with the LR gone. Then I would still recommend slowly introducing your fish back into the display. Do you have any friends or is there a local reef club or LFS that you could use as a resource to maybe hold some of your fish while you get things in order?
2) Did you have all the livestock for the entire 1 1/2 months you were running this tank without any problems with ammonia or nitrite?
3) What biofilter are you using for this tank besides the live sand?
<b>The LR:</b>
Did you follow the cycle in the curing bin? It doesn't sound like it had finished cycling when you put it in the 135. You should make sure it is fully cycled in the future before you add to the main display.
<b>The 20 gal long:</b>
Whoa, that sounds like too many fish for this small space. I think the space in the 135 is really needed to keep the agressive fish from being too aggressive. In the 20 you are likely to have mayhem. I recommend either returning many of the fish to the LFS or having some experienced SW aquarists hold them for you.
<b>The fish:</b>
I do not know enough about the fish you have, especially the trigger, and I don't know how compatible they are together. Also, the tangs and the trigger generate a lot of waste (amonia).
<b>The Future:</b>
Take things slowly. If you have been adding fish since you got the tank (1 1/2 months ago) you have been going way too fast.
There are some excellent threads started by WaterKeeper that could really help you out. I recommend reading as much of these as you can. They are listed in the second post in this thread:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=166836
Jack