re. Priest becomes a Muslim
I'm inclined to think that becoming a Muslim would require little more than simply being disenchanted with one's Church being (perceived to be) under the thumb of worldly rulers.
re. Government involvement in Orthodox Christian affairs
There is nothing new about this really. If meddling rulers were enough of a reason to jump ship (either for a schism or another religion entirely), then there shouldn't be an Orthodox Church at all. There's a nice big chunk of Russian Church history (following the dissolving of the Patriarchate) which while not entirely unhappy, makes any meddling by the current Russian government in Church affairs seem as nothing.
re. Islam "fastest growing religion"
I've heard this many times before. I don't doubt it, if only because Muslims actually have large families. I also think citing the number of nominal Christians as opposed to nominal Muslims is a bit misleading, if only because the term "Christian" covers a very wide spectrum of beliefs, whereas Islam is not as torn by sectarian divisions. Islam (at least in it's dominant Sunni form) is non-clerical and non-denominational. I'm persuaded to think that while there is certainly alot of mediocrity and lukewarmness amongst Muslims, it's probably not as "dire" a situation as it is amongst those persons demographers would lump under the label of "Christian."