Does wise practice of compassion ever lead to suffering or bliss for the practitioner?
Yes, the Brahmavihar compassion is meant as an antidote for jealousy and feeling of being rejected/wronged by the world. Generating compassion puts one into an elevated position, so one can feel better.
Is there a difference between compassion cultivated through the Brammaviharas and compassion cultivated through Vipassana insight?
The realization-induced compassion is spontaneous and more authentic than the generated.
If one is enlightened does that mean one is compassionate or fully compassionate?
Perfectly compassionate. Which among other things means that one sees Samsara as Nirvana.
Why does wisdom lead to compassion or compassion lead to wisdom?
Wisdom leads to compassion, because we clearly see how foolish people suffer from self-inflicted trouble. We see how they entangle themselves in difficult karma due to pointless goals they saw as important. We see how people expect things to last despite the impermanence.
Compassion leads to wisdom, because it's a practice that helps one detach from the egoistic concerns, disentangle, and achieve enlightenment.