That pool closure is going to be a pain in the arse for you - she imply's there's somewhere else nearby, is that an option for you?
Realistically, you cant actually start training untl the 2nd week of October, because I dont think you should do anything any sooner than a week after your ankle comes out of its cast. Apart from your physiotherapy of course. Do tell your physio what you intend to do, because its important you dont bugger up your ankle forevermore trying to do too much too quickly.
IMF is my first (that implies more than one!?) IM, but I trained myself up to the Little Woody from a VERY weak swim base and precious little more biking, but with a good run background, in 3 months and finished it in 6hrs 38mins. So I think its possible. But I was also writing my thesis in a very leisurely fashion, so had zero work committments, and we have no kids. So my time was my own to train.
You asked a few pages back what, if anything you should be doing now. I'm no expert, but honestly, I would say the best thing you can do for the next month is spend a lot of time with your children and husband, because you're not going to be seeing much of them after that. Oh, and save your money, because equipment is expensive. There's no point in panicking about things like Open Water swimming yet, because you have months and months ahead of you, and far more important (but not insurmountable) goals to attain waaaaay before you need to worry about that.
But, like I said, I'm a novice, so what do I know?
Did you buy the cancellation insurance?