Natric - I don't think you can sole source while breastfeeding. I remember how exhausted I often felt when I was breastfeeding and that was eating normally. You'd really have to discuss with a counsellor but I expect that if they accept you at all it will be on one of the higher calorie plans.
As for keeping the weight off. Well, my counsellor has. She lost 3 stone about a year or so ago and is still slim. She still drinks loads of water each day - that way she's not tempted by sugary drinks, and it helps curb her appetite. She eats normally now, but is very aware of portion sizes and tries to eat healthily for most of the week, with just 1 day of treats at the weekend, instead of a takeway several times a week. All sensible stuff, and all stuff we know (or should know) how to follow. Personally, I am hoping that the incentive of being 9.5 stone again for the 1st time in god knows how many years will be enough to keep me in check. I intend to cut back when I notice a pound or so gain, rather than simply moving into "big" clothes.
I'm very lucky because I have 100s of pounds worth of clothes vouchers to spend. This is the legacy of birthdays and christmases from about the last 3 or 4 years, but I have always vowed only to spend them once I got the body & weight I wanted (I have been living in cheap Tesco jeans because I didn't want to spend more than I had to on "big" clothes). So ...... that will be another incentive for me, because I will want to stay in my lovely new clothes.
Fact is we are all larger than we want to be because we ate too much and/or didn't exercise enough. If we carry on like that afterwards we will get large again. I think eating healthily is vital and TBH, right now, the thought of eating healthily - or eating anything at all - seems wonderful. Maybe I am torturing myself, but throughout this I have read loads of cookery books and storing away healthy-ish recipes to concentrate on once I get to goal. For example, it is possible to make passable chips in the oven with just a very fine spray of that 1-cal oil, making sandwiches without butter by using very low fat mayo or tsatsiki instead ...... that sort of thing. I really think that's the path I am going to have to try and follow when this is over, and plan "treats" once or twice a week only, because, unfortunately, I'm not the sort of person who can just eat 1 square of chocolate a day !
Hopefully, going through the CD maintenance plan will help me stick to that. My counsellor also said to keep telling myself that getting to goal is your investment in yourself. Not only will you have spent a fair bit of money to reach that point, you have also invested in your health, so it would be awful to throw that away.