Hi there
I bottle fed. I always gave the day feeds when due and then the BT feed whenever BT was, often this would mean there was less than the full amount of time between E but I didn't worry about that. It doesn't seem to me that the feeding is going to be what's causing the NW. It is totally normal for a bottle fed baby to still be getting a night feed at this age, many people who follow EASY do a dream feed but if you don't dream feed then it's an awake feed at whatever time LO is ready for it in the night, which seems to be what you are doing.
If you wanted to try something a bit different, for your peace of mind perhaps, you could give that 5.30 E a bit earlier maybe at 4.30 which is only 2.5hr from her last E but then gives her a longer time between the 4.30 E and the BT E. She may take less at the 4.30 and more at the BT... although it is not really that long off before you can start to wean the night feed (maybe around 7-8 months) so she will then take all her calories in the day.
Mine was also on 25th centile (between 9 and 25th throughout his first year, now more like 25th for weight and between 25th and 50th for height), it does not indicate a need to try to make her eat more, it just means she is a smaller person. The centile line they follow is neither good not bad if it is higher or lower, the only thing that matters if following the line (moving one line either way is also fine).
WRT starting solids - I have come across LOs whose sleep goes a bit off track, gas or wind, pooing at the wrong time or just being over stimulated by all the new flavours and textures but I wouldn't worry about it. If your LO does experience any of those it will settle down quite quickly unless as Scottishmummy said there is some sort of reaction.
hope this helps some