The cleanse will probably help with the weight thing, but be sure to accompany this with probiotics to replace what intestinal flora you will lose during this period.
Re: orthotics, due to your lapse in fitness I would procede very carefully, starting with walking, not running. The orthotics can't possibly replace the stability you've lost, or compensate for the weakness you may encounter on cleanse. Whatever you do, take your time doing it.