Without actually having said fabric in my possession I really can't say positively what I would do.

However, here is what I do when faced with interfacing choices:

Cut a 6-10" strip off one end of the fabric, and cut it into 6-10" squares. Then pick out whichever interfacings you're considering and try them out on the squares. Whichever square gives you that 'hand' you were envisioning for your project is the one you use. Or if one is not quite right, you build from there.

If the fabric is 100% wool, lightweight, but lots of stretch. I would not consider fusible interfacing. To apply a fusible properly, the wool will shrink and you'll end up with bubbles or wrinkles. You could of course pre-shrink the wool if you were dead-set on fusible interfacing. And contrary enough, some fusibles need to be pre-shrunk as well.

Your solution may actually be that you'll need to pre-treat your wool and use a sew-in interfacing. You might want to steam press that stretchiness out. One method is to steam iron by lightly pressing and then holding the iron about 1" above the fabric and steaming. Or there's the London shrink method, where you roll your fabric in a damp sheet, let sit overnight and then lightly steam press (that's pressing, not ironing). Once you've done that, your interfacing options might change slightly.