Micheline ... I'm sorry you are having these problems. A PEG tube is a great idea, but a colostomy seems extreme, unless there is colon cancer present or other urgent medical issues. I don't know your medical history, but if constipation is the "issue," there are many remedies. The muscles in our colons are among those that weaken with
ALS, so we have to get crafty and get control back with other means.
My mother had a colostomy, and they are much more difficult to handle than a PEG. If you need one to save your life, that's one thing ... but an optional one for a minor matter is another. Plus, resectioning the bowel is a long, complicated surgery, and with an FVC at 65%, I think any surgeon would be reluctant, except as a life-saving measure, and even then might consider the surgery too dangerous.
Good luck tomorrow.
Perhaps I am misreading your post. If I am, I apologize. If I'm not, then I'd suggest going for the PEG as soon as possible, and talking to your doctor about remedies for your other problems.