Answers to your questions:
1) Never peel the figs. Just cut off the tip and any odd stem-ends.
2) Because you're not using pectin, you can be a little more cavalier about proportions. For instance, you can put in the 5lbs of chopped figs, then add another pound of another kind of fruit. Again,unless you're putting in something with lots of protein or enzymes (citrus, mango, papaya, kiwi, pineapple) the only thing you have to focus on is the viscosity.
3) Meyer lemons will work just fine for the acid.
Finally, the way you test your jam for "jell" qualities is put a teaspoon of the hot fruit on a ceramic plate (that's been chilling in the freezer for at least 10 minutes) and let it sit for about 5-10 seconds. Then, tilt the plate. If the fruit runs, it needs to cook some more. If it solidifies or at least holds in place, that's the degree of jell you'll get once the jars cool.
Good luck!