Being in the same boat (old and creaky body), the best thing that will help in reaching the G string is to swing your left elbow under the violin (and maybe even past it a bit, if you can get it there.)

That won't be easy, either, but it's easier than trying to twist my wrist around 270 degrees or something.

Check out the home page of this site. Pierre (Fiddlerman) has several introductory videos, including how to to hold it.

Everybody is different. Expect to have to do some experimentation to find a combination of violin position, chin rest, shoulder rest, and body position that will work comfortably for you. There's no magic answer that works for everybody.

A couple of things I didn't know at first:

• It's ok to partially hold the violin up with your left hand. Also with your chin/jaw, and the shoulder rest. Don't hunch your shoulder up, and don't clamp down with your head. (In general, don't do anything that hurts, or takes lots of force (because that will hurt soon).) Otherwise, experiment.
• It's ok to move the violin around some, and use different ways of hold it up at different times. In fact, it's encouraged, because moving things around and taking pressure off of them once in a while decreases/prevents tension. (Tension is probably the number one enemy of things sounding decent.)