I might be late to the party.
Great piece! Lots of effort put into this and you pushed yourself. I can tell.
Lets see if we can push your image a little further and you can take some stuff away for future projects.
Consider how your viewers are going to see your final image. Will it be print, phone, monitor, web, forum, tv screen? Old painters considered how far away people were going to stand from a painting, and we should consider this in our own modern way as digital painters.
I snipped this version off of my browser just so I could see the whole image. It's probably me and my 'old thyme' 1080p screen but i couldn't see the whole image scrolling through the forum Maybe if i was on an Ipad....but I don't own one.
If we look at the image as a whole, the tree is obviously the focus. It is THE force in this image.
And to me this is getting into mural on a wall size print territory. Like a huge wallpaper sticker thing you know?
Looking at it....Do we need to be up in that tree? Is there something we are supposed to be seeing up there? Were you doing a tree study or kept adding space to the canvas accidentally and had to fill it?
It might hurt really bad. But as an art director I would say, "can we just crop it to this?"
I would continue to say, "This section is PERFECT! It's where all your love and time went, it has everything! Primary, secondary, tertiary focus, depth, story, It's great! Can we just show people this? Or is this tree really really important? "
HOWEVER if it was a book cover I could totally see it because you would need that sort of space for text.
But I don't think that is what you were trying to do.
lastly lets address the color, by adding some simple adjustments in photoshop. Lets bring up the yellow overall in the image, adjust the contrast and add some blue into that tree with a gradient set to overlay and opacity brought down a bit. The sky color is going to bounce around and be your reflective light everywhere.
I also see that you tried to do the light through the leaves thing and you had the right idea just had to push it and not be afraid of making the shadow.
Hope that helps. Again great follow through.