I have a potted lemon tree with a couple problems:
-Soil barely has any structure
-Infested with scale, ants, sooty fungus
-It is supported by a trellis that I'd like to remove, but I don't think a lot of the limbs are structurally sound on their own.

I've had it for more than a year now, but haven't always done a good job caring for it. It's the first plant I really tried to keep, so inexperience has been limiting what I could do. I consider myself lucky it's still alive.

Because of the scale, I've already pruned a lot of the branches that were weaving across the middle of the tree. For the most part I'd considered eradicating them a priority, though now I realize the tree desperately needs some fresh soil.

My question is, what do I do first? I have hort oil (except that last time I tried to use it, the spray bottle got clogged and stopped spraying) but the tree is still alive and producing as usual, and the flowers are almost open.

And I'm not sure how to get it from the pot either. It's ceramic and between the pot and tree it's fairly heavy.