Well, 80 Sathanases can cause a supernova. I don't think 80000 Demons can do that.
As for the Colossus, they don't want to lose another jump node - ships can be rebuilt, as far as the GTVA know, jump nodes can't.
I wouldn't risk cutting off everything beyond Laramis. I'd much rather sacrifice a ship that took 20 years to build. And why would using the Colossus ensure one obliterated planet? It takes 13 hours to bombard a planet. I'm pretty sure the Colossus can kill a Lucifer much more quickly than that. It can probably intercept the Lucifer so it can't bombard the planet anyway. There is no reason why it would take that long for the Colossus to respond. I'm pretty sure that it can cross GTVA space in a few hours (15 minutes per jump, probably less judging from how fast the NTC Napoleon leaves the Regulus node in Rebel Intercept (INSTAJUMP)). Your scenarios are inherently flawed - it should be (assuming success):
1. Bombers attack the Lucifer in a Node.
Best case scenario: One unimportant node gone, no way to replace.
Worst case scenario: One critical node gone, large part of GTVA space cut off permanently. GONE. FOREVER. Say goodbye to 2 billion citizens, four star systems, 6 installations, 4 full fleets, 2 shipyards, everything. Gone. Forever.
Best case scenario: Minimal damage to Colossus.
Worst case scenario: Heavy damage to Colossus. (Major repairs or scrap). Even if the Colly bites the dust, it's just going to be at most 20 years for another one. By that time you'd probably have better technology and can make better ones, and build them faster.