Helenemjay, the ladies here have given you great advice. As regards the HV bottle suggestion, the only reason I imagine the HV suggesting that is to fill up your dd so she is content and does not ask for a feed for a longer time. But as you found it, it is false economy when you add on the time of preparing bottles/formula, cleaning up and on top of that, your dd is screaming one hour later! It is a common misconception that bf-ing is about nutrition. From a baby's perspective (at least my dd's) it became increasingly more about comfort than nutrition as she got older - until we got to the boobie in the mouth stage for napping because of her teething.
Merryberry, I am totally in awe of you successfully putting your ds on the Baby Whisperer EASY routine (meaning Eat, Activity, Sleep, Your time). That book left me in tears because my dd was determined to march to the beat of her own drummer - she was a very poor sleeper, feeder and nursing addict. Her routine (as dictated by herself) was bf, sleep, activity, bf, sleep, bf/sleep, bf/sleep, bf, activity (in any order). If she wanted to sleep after a feed, she could not be woken up and once she was awake, could not settle without another bf. This falling asleep from awake thingy never happened for me - she was hysterical on her back in a cot within 3 seconds.
Helenemjay, I don't want to scare you. My dd is a bit of an extreme example. But I see a lot of myself in your descriptions - I was trying so hard to make life easier for myself by following advice from books/HV that I could not relax and enjoy baby. It was only after I threw all advice/warnings of bad habits and rods for my back to the wind that I finally was able to just go with the flow of my dd's eccentric demands.
There was a lot about dd's baby days which was very hard. But I will always take away with me the peace and calm of those long bf-ing/nap sessions where she lay in the crook of my arm, I had my feet up, and my other hand was surfing the net!
I am truly amazed you are able to juggle the demands of 2 other children with that of your cling monster. Perhaps a different tactic would need to be used after 3 pm. You are doing great - your dd is so special, she really is.