A103
Psi-magic transparency is purely up to your DM, but there's a problem in that the reserve mechanic involves having the spell prep'd but un-cast, and Psi doesn't prep in the first place. Also, few powers have the [Fire] tag and those that do only have it roughly 1/4 of the time. Possible house-rule: you can use the reserve feat after using a [fire] power of the appropriate level.
Q104
Let's say you're a level 20 Cleric, Air and War domains, everything else open to customization.... and you want to build a bomb. What do you do?