If the settlement amount is mentioned in the mutual consent petition, it will be difficult for husband to back out. You can also mention that in the event the husband defaults to pay the amount at or before the second motion, you can proceed with the contested case. Also, in case he does not pay, you can withdraw your consent at the time of second motion.
As regards the jewellery items, you may take your own appraiser to the lawyer's office to ascertain the weight, quality etc., and sign the letter only after your full satisfaction.