Suggestions:Maybe you could add another tier or two on top of existing thermal expansion items. Think energy cell that could store 1 billion rf or conduits that could transfer 100k rf/ t. These would all require endgame items from your dimension of course.
Another idea I had was needing the mob drops from this dimension to be charged with rf to be able to be used. You could also add boss monsters in this new dimension, possibly variants on the wither/ender dragon that have been tainted by the exon's experiments...
I think on top of the 10 million required to open the portal, there should also be some sort of constant drain for balancing reasons, just to make sure people don't get there without a stable rf supply. End dimensional gateway could be crafted with the end dragon egg, nether one with wither star blocks (9xwither stars), and overworld with diamond blocks.
Hope you like the ideas, looks like an awesome mod already