New to Sewing -- have a dozen questions...

[GreatGazoo]

I bought a machine about 4 months back to repair sheets, hem curtains, etc. and started making clothing. I love it. It is a challenge to think in 3 dimensions and putting it all together is like doing a puzzle.

What is a good place to buy fabric online? I have a JoAnn's locally but their selection seems to be cheap and more oriented toward quilters. I am looking for high quality flannel, all cotton knits and organic cottons suitable for sleepwear and light weight clothing.

What are good alternatives (for finishing seams) to pinking shears? I remember as a kid thinking that it was odd that all the uncomfortable parts of clothing (the seams, serger threads, etc) are on the inside, against the body.

The machine I bought was $70 (a Brother 2517). I really want to invest in a decent machine that I could use on heavier fabrics and for more precise work like piping, flat felled seams, silk, linen. I will be buying the feet for piping/zipper, rolled hem and others but I don't want to buy feet for the $70 machine if I am moving up. What machine(s) are good for making custom clothing and alterations? What is a good machine at $300 or at $700?

I see there is software to make your own patterns (or customize from templates). Is there a machine that will cut fabric directly from computer designs? I found some that cut 12" pieces but really want something that can cut pants and shirts, something that will work with the whole width of the fabric so about 45 inches or so.

Is starting and ending with 4 backstitches enough or should I be doing something else to the ends of my thread?

What kinds of fabric are challenging to work with versus which are easy?

Is pre-washing fabric absolutely necessary, especially for cotton?

Thanks for any help!