Pretty good job, but IMO (and I may well be wrong!) the inner limbs aren't quite working enough (but it's only a tiny bit stiff) , which is why you are getting some set in the mid limb. As you say lower limb is a tad weak compared to upper.
Lower limb looks a fair bit shorter than the upper... I know this is generally the case... but there is nothing to say it has to be that way. I've made a couple of bows with the lower limb longer and they've both been good shooters.
I'd say leave it alone, now't much you can do without losing weight.,
Del