My "fear" is that if I become unavailable, he will start hanging out 'platonically' with women when I can't see him; and then god knows what would happen.
I think that's true to a degree. This is not the time to shut him out and play hard to get. But it doesnt mean that you have to sit at home waiting for him to call either.
How about: act like you are (monogamously) dating someone, at the "initial" stage. You still might do things "on your own", but: a) you wouldnt do something that you wouldnt want them to know about b) you would probably be open to them coming with you and sharing the experience.
Soooo... think of fun things for you to do... make plans for them... invite him.. and if he comes along, have a great time together, and if he doesnt, have a great time without him
That way, you are clearly not "unavailable". yet at the same time, you are not "dependant" on him either.
My current status: june 2006. Wife ran out and filed D. Finalized Jan 11, 2010, after 12.5 years M. 3 wonderful sons caught in the middle