The photos are difficult to give a critique on because they are so small and the horse isnt standing properly for a critique.
From what I can see, the mane thing that stands up to me is the angle of her back legs, I'll assume is just poor standing position in that particular photo and not a problem with her build or other condition.
Her head and neck are not proportionate to her body. I don't find her build downhill as much as it has been described. I do find her a it long tho.
It is difficult to give much more for critique due to the poor quality of the photos. I strongly recommend just getting more and posting them on here.
About her mane and tail. I have no idea what to do but keep them brushed and washed. Tips would be helpful.
Her knees are not crooked its just that picture and I will try to get more piccies.
I can do very little about photo size as the photos are taken with my phone, although I may be able to hire a digital camera and get some decent ones.
I am aware she needs work on her topline but because of the horse flu very little work has been done.