Try to realism is drawing big like on the old canvases and mural walls, patiently, forming an inner dictionary of curve and mark types, length units, etc. The classic o'clock trick should help, for example a like of gentle sloping hill may be 2oclock or half past 2 etc or more advanced as you improve. Classical trick of curves is noting the certain types of curves of your hand and say fruit. Between each line give yourself some time to think, pause 5 seconds between each line if it helps and maintain you don't just understand shapes but forms and how they relate to each other in space. Study from pictures, not books, take what you need from photos and real life and art and apply it to your own inner manikins, your own inner imagination. There was an article on another forum along the same lines. If you want to study realism (which is great for learning advanced colour, you can check out free forums like on parts of ConceptArt Forums for exercises and challenges.
Studying and creativity make the artist, working from imagination, reality and memory until you need references no more.
SAI paint tool costs but not too much, it is what most digital artists tend to use unless they work in big companies or colleges and in that case they use Photoshop etc.
Providing you have a tablet or even sketching, try to draw from your shoulder, it will free up your lines, let your arms sweep across the medium without touching and land to continue the line as if on a runway. Have you tried the CtrlPaint website? They provide great tutorials even though much is geared to photoshop it's not hard to catch the jist and as what the instructor says about the interface applies to not just PS but whatever you use, I believe you may find some help in composition with Concept Art and ImagineFX as well as dA-renown Schoolism and Imaginism. Try to work on your creativity at the same time, experiment; leave behind what methods don't work, find an artist who's similar to you and assess why theirs is better than yours in certain respect and use art theory to understand the differences.
You'll find your mindset and work patterns changing over time, if you want to improve don't be too conservative and too afraid to experiment as all that will do is halt your progression. Visual Thinking, well if you don't go to art school, iTunes U has some very nice art theory, thinking help and history. Trust me, you'll be surprised how much furry artists take after art school principles. Studying "gesture drawing" may help you expand your poses a bit, long as you don't trace models and form a dictionary based on an inner manikin. Study line efficiency and fur layering if you continue to get like issues, remember that you don't need to emphasise surface detail with heavier lines but rather hint at it. You're doing well, give yourself a hug
