Hey Pam, lots of stuff to consider. I'm also extremely lean (very little BF) but low on LBM with anything between 7 - 10kg to gain (scary). It's a slow slog to put on LBM if you start out lean so patience is key.
You should aim for 1.8-2g protein per kg of bodyweight as a starting point but the ratio of fats and carbs is a very individual thing and you should experiment with what works well for you. Don't forget to give it time. I'm still trying to figure it out for me.
Limiting refined carbs is a good thing from an overall health perspective but probably won't make too much difference to your body composition result.
You certainly do not need to be eating every 2-3 hours UNLESS this works best for you to get the kCals you need for the day.
Have you worked out what your maintenance kCals are for the amount of activity you are doing? You should be aiming for a surplus of kCals if you are looking to put on LBM ... you could start at around 200-300 above and see how you go.
As an example, I'm 158cm tall and weigh around 44kg. I had a DEXA scan a few months ago and found I had very little BF at all, but also am way down on LBM. I also workout around 5 days per week and my maintenance kCals is about 1770 per day. I'm currently aiming to eat around 2000 kCals/day.
I used to eat 6 times per day but have now shifted back to 3, occasionally 4 depending on the day. This suits me better at the moment.
I try to have more carbs on my training days and more fats, less carbs on my rest days, although I'm not measuring them anymore. I tracked it for a short time to get a better sense of my intake and now wing it with some confidence.
I make sure I get the necessary levels of protein every day too. Still waiting to see if this will work. If not, will try something else.
It's all very confusing because there is so much conflicting info out there. Ultimately, different things work for different people and it all depends on your goals too.
I found getting a DEXA scan made things much clearer for me in terms of being able to set goals and understand the magnitude of the task.
Not sure if this helps?