I have been through all of this myself Julia and in the end, no matter how close you are to Witness friends, the religion will usually divide people and you will go your own way and they will fixate over something or someone else. I had many long term JW friends (I think they were friends) but the religion is the very thing that divides us and as with me, in time you will be amazed at how much you have changed and moved on and how they have remained the same.
Whenever I meet an old witness 'friend' in town I am truly astounded at there being no change in them. They do not seem to grow and it is the very organization they follow that, out of its own insecurity, prevents its followers from advancing for fear they will out-grow the leaders.
We had an elder in our congregation who said that " sometimes, the best thing to do is to do nothing at all". That is probably the best piece of advice I ever heard at a Kingdom Hall and I applied it when leaving the JW's.
In short, you could argue/correspond with them from now until doomsday to no avail as people will believe what they want to believe and if they are to see the truth about the truth then they must do it in their own time.
I think it is hard for them because, as they watch you leave, they somehow feel that they are being left behind which, of course, they are.
I wish you the very best.
erbie