L.,
First off - congratulations to you - what a wonderful thing you are doing for YOURSELF! Lots of kudo's to you for taking care of yourself - most of us mom's do not, me included. You deserve so much praise for the dedication and hard work you are doing for yourself.
Now, about your post. I do not think that you are off base in thinking that people are rude. True, some of those comments come from the heart and people do not realize that they are being rude. I think you are handling it very well with your remarks. Graciousness is the best comeback. I know it hurts but there is no way to stop people from saying stupid things. Just keep up with the "thank you, I am happy with my progress and while you have some good suggestions, I am working on a specific process. I am in this for the long run. Thanks for your advice though" and turn the conversation over to something else or leave. You are doing a great job - do not forget that.
There will always be insensitive people out there - no way of getting around it but being gracious on your end will make you feel better and keep you on track in the long run.
Again, good job!
L.