How to kill Bugzilla: take Veteran & Scientist (+20% damage) with you, buy the alien gun and 100+ charges, max adrenaline and medkids. Only use second attack (kapoom), heal HP and drowsiness when necessary.
No, it's not that hard to get the 26 gold souls, just work a bit on your strategy. The more splitter demons, the more useful gets the worms block. Grab the quick demons with grabber blocks. And what is especially useful: build only a medium high tower (2-3 blocks) as your standard fighting position. My survival setup: 1stRow: sticky/magma/grabber/eye/sleeper 2ndRow: - 3rdRow: grabber/sticky/worms/standard fighting position 4ndRow: - 5thRow: sticky/magma/grabber/eye/sleeper 6thRow: - 7thRow: grabber/sticky/worms/worms/worms