Great improvements!!!!
Here's some answers to your questions:
1) How to handle nights. My rule was always cat nap if their A time would mean putting them down for cat nap at 5 pm or earlier. If the A time after last nap would mean a cat nap after 5 pm, then I would just go for an early bedtime. IN the instance you gave, where she woke from nap at 4:30, that would have meant her A time would have not made her sleep until about 6:00 (1.5 hours A time). IN that case I would have just made 6 pm her bedtime.
As her naps get a bit more consistent then you'll have room for a catnap. The most important thing is honoring those A times. When you have a late cat nap it just throws the whole night off. In your situation, you tried putting her down for a cat nap after only being awake for an hour! No way was that going to work, which is why she didn't fall asleep until 6 or so.
2) Yes, if she's hungry at 5 feed her. But treat it as a night feed, meaning you feed her in the dark with little to no interaction and then just put her back to bed. Hopefully she will then sleep until 7:30 or so.
I'm hoping that 5 am feed will disappear as we get better day sleep in her. I suspect she's waking b/c she was OT at bedtime and so that makes her wake at 9-10 hours after going to bed. If she gets decent daytime sleep in her she won't be as easily roused early in the morning and *should* be able to make it to 6 or later without a feed.
Are you doing a DF at this point? If not, this a great time to introduce one. That will DEFINITELY help her make it thru the night! We usually advise using a DF up until about 7 months old or so.