You don't have enough to blow up a pyramid at the moment. Any of the pyramids.
Natasha utilized her unique understanding of fluid mechanics and the transformation of liquids to solids and back again as well as her connection to the Ancient Widow, mixed with remarkably successful infiltration efforts to achieve the superlative result she did.
The bombs that Frederick is making are dependent on what Hultressa can squirrel up, it's not so easy as dipping into the local black powder stock, because the Drucchi doesn't have any. Frederick is basically having to alchemically produce the black powder by hand, then place it into containers, treat the wicks and like, and then set them aside.
Basically, at the moment, you have a good handful of pipe bombs/roadside IEDs. You do not have building-breaking C4 levels of boom. That would/will take a lot more time and resources - because again it's not simply restricted to Frederick's ability to produce but Hultressa's capacity and ability to acquire the ingredients required. It is in fact the latter which is the true bottleneck, not Frederick's ability or personal attentions.
Furthermore, you do sort of need someone to, you know, plant said bombs into the pyramids if you wanted to have a go at them. N+R+J are currently in an aquafarm, plus their little band of supporting slaves. Hultressa could, quite possibly, secret some bombs here and there, but still.