Hi Rose, I'm sorry to hear you are having such a rough time of it... I am also a long-time Photoshop user (15 years), and was also an Adobe Certified Photoshop Expert at one point.
Coming to a node based workflow was somewhat new to me when I started with Substance Designer (v1.0), and I got very comfortable with it by the time I taught the VTC series (v2.1). So it is certainly possible to come from a Photoshop background and get along with SD very well -- in my case to the point where I was able to drop Photoshop for 3D texturing entirely.
I would have 2 questions for you:
1) Is it the non-linear aspect of the nodes workflow or the nodes settings themselves you find more difficult?
2) Have you watched these tutorials:
http://www.youtube.com/playlist?list=PLIbMNGfLdtRDpkuP_lcx_yCqVaZxUxRdYThe reason I ask is that free tutorial series goes over the nodes in depth and features quite a bit of information about the new(ish) bitmap painting features -- which as a Photoshop user you should find very easy to use.
The reason I reference my youtube playlist is becasue while the same tutorials are available on this page:
http://www.allegorithmic.com/tutorials/first-steps, becasue of the way that page is designed it is very easy to miss all the good stuff hidden in the links at the top (Atomic Nodes, Bitmap Node, SVG Node, etc.) .