1. To make an oval, chain, crochet into your chain, and when you reach the end put 3 sts into the last chain. Then simply continue crocheting into the other side of the chain. Again, when you reach the end, 3 sts into the last st. Just keep going.
2a. Yes, each square on the chart represents 1 sc.
2b. Yes, you should be able to use a cross stitch chart with success.
Here's a quick test I learned today that'll tell you one way or the other: take a few inches and roll it into a ball. Wet it and add a little soap, then rub it together between your palms for about 3 minutes. Rinse the soap, and see what you've got.