Please don't worry about asking questions - when we were going through this I had some wonderful support from people on here who were very frank and honest with me about their experiences, and it made a huge difference. If I can repay the favour in some small way by answering your questions and helping a bit than I'm delighted to be able to do that!
You may not think you're being brave but you really are - you're getting through this one hour, one day at a time which is all anyone could expect, and you're managing to think of your little girl at the same time and take care of her, and consider her best interests with bf, so you ARE being extremely brave.
As for what to expect tomorrow - I don't know where you are, but we were in Bristol at St Michael's Hospital and I can hand on heart say that we were treated with great kindness, sensitivity and care by all the staff involved. They were extremely considerate of our feelings, I hope you have the same experience. I found it's like any difficult experience - the anticipation is worse than the experience in a way, once you're engaged in it you just get on with it, because you have to. And you're dead right, the decision is by far the worst part - it's such a huge decision to make and there is no right answer, which means it's absolutely terrifying.
Afterwards I felt a mixture of relieved that it was all over and deeply sad. I never once felt we'd made the wrong decision though, and in fact when we left the hospital the sun was shining and all the blossom was out on the trees and (this might sound daft) I felt like we and the baby had been released from all the stress and pain of the previous couple of weeks, and we could start to let go. Obviously it took quite a bit longer than that to feel over the experience, but it was a hugely positive moment in a way. I hope that makes some sort of sense.
You haven't mentioned what your diagnosis is, so I won't pry, but as for further tests, I've just remembered we did have one....our baby had a very serious heart defect, and they tested a skin biopsy afterwards for a rare chromosomal problem with could have caused it, as that would have raised issues with having further children. Luckily it was negative, and we have been told that there's no reason we shouldn't have a healthy baby this time (scans next week gulp!), so it is perfectly possible for these things just to be a one-off. And like us, you already have one healthy child which is a big positive, as it makes it less likely that it's a recurring problem, iyswim.
Hope you have a lovely day with DD and I'll be thinking of you. Be kind to yourself and you will get through this - I'm living proof that you can come out the other side in one piece.