I basically agree with what MattsBettas has said.
1. I use airline tubing when my fry are young to do water changes, but even then I still will end up with one or two fry in the bucket. I always make certain to go over the bucket with a strong light to make sure I don't tip anyone down the sink.
2. Like MattsBettas has said, you don't literally do a 100% water change on your grow-out. You don't want to be moving your fry around needlessly, especially when they are younger and a lot more sensitive.
3. I have done plenty of partial water changes when the fry were still in the nest being tended to by the male, and I haven't lost any fry. However, I think it is best to slowly just add water at the start, rather than try and do a traditional water change. If you are concerned about debris on the bottom, you can always use a turkey baster to carefully suck it up.
4. I tend to feed and then do a water change a couple hours after once everyone has a full stomach. However, it's really up to you, and as long as you are not leaving food (particularly microworms) to rot on the bottom for days at a time, you should be fine. Based on my experiences, I find it generally takes a day or two before you start to see signs of live foods like microworms decaying.
5. There is not set number for how much needs to be fed and I wish good luck to anyone trying to count out the right amount. I honestly think it is best to slightly underfeed than slightly overfeed. So be conservative at the start and if you think your fry look hungry, you can always add in some more.
I agree that microworms are a poor choice of food. I only use them when my fry are too small to take BBS. They are not very nutritional and have been linked to ventral fin problems.