Unless you believe what Trump claimed, that Comey told Trump he personally was NOT under FBI investigation. Even if he is, as President he can discuss that information with whoever as he sees fit.
I see your concern that you view Trump aiding the Russians, especially if you view him as a Kremlin puppet. But this exchange of information with Russia is hardly new. If Trump gets Putin to help leverage North Korea to disarm their nuclear program, and to slow down or stop Assad, perhaps he justifies giving Putin something in return. Putin's assistance could be quite valuable.We aren't a fly on the wall. We don't have the Intel info that Trump has.