Once it reaches the 3 tomoe its stays like that since it is fully mature. Wouldn't really make sense to go back to one tomoe.
Yes one can go to MS and back to 3 tomoe, has been seen to be done by itachi and sasuke. Seeing how kakashi blacked out when the Ms activated he may have forgotten or...
Its the muslim extremist who have made a bad image to their own religion. The rest have no fault in it and just want to live a normal life with out being judged for the actions of others. Also the conservatives of the U.S are ignorant for judging others but yet get offended when they are judged...