Hello from California! Your questions are great! Here's my input:
Either basting or pinning works great. I prefer pinning and use the curved Quilter's pins. I pin every 3-4" across the quilt, or I rest my closed hand on the quilt, and place a pin every so often, about the width of my hand.
I now have to pin on the floor, as I don't have access to large tables. Some quilt shops will let you use their classroom tables to pin if you ask ahead of time.
I stopped quilting in the ditch years ago and now stitch 'beside the ditch' exclusively. It's quicker, less hassle, and adds a nice finish to a quilt, especially if you use today's beautiful variegated thread.
i think quilting 10" apart would be a bit skimpy, but it really depends on your likes and the design. I stay away from quilting quilts 'to death' because I think it defeats the purpose of a soft, usable quilt.
And finally, I think it's possible to finish by the holidays!
good luck to you! Post a pic when you complete your quilt!
V.