Regarding your questions how to offer respects to Sannyasis. Every Sannyasi, even if you see a Mayavadi Sannyasi, offer him your respects—there will be no harm. As you have observed we shall follow Lord Caitanya's instruction that we give all due respects to others regarding their position, but there is no need of always associating with each of them. Even if one is Vaisnava, but not of good character, we can give him the Vaisnava respect, but we cannot associate with him.
Regarding how to act when there is a choice of either attending Aratrik ceremony without bathing first or bathing and thus missing attendance at the Aratrik ceremony, the answer is that the rules should be followed as far as possible. If it becomes necessary, simply wash your feet, and when possible also wash the face, head, hands, and rinse mouth with water.