There are still many of us out here who accept Medicaid. The criteria remains the same as with any other insurance. You will need to demonstrate symptomatic macromastia ie neck back and shoulder pain, rashes, bra strap grooving, etc. The amount that needs to be resected will be determined by the Schnurr scale.
The biggest barrier to you getting a breast reduction is not Medicaid but is your weight. At your weight, you will have more issues with wound healing, seromas, etc. also, depending on the amount that needs to be removed, you may require a free nipple technique which completely removes your nipple and then places it back onto the breast in the same fashion as a skin graft. Your nipples will be insensate and have a higher probability of partial loss.
that being said, a breast reduction is still a great operation if you are suffering from the effects of having giant breasts. You can use this as a stepping stone to embarking on a healthier lifestyle in order to lose weight. You will find it much easier to exercise without having to deal with huge breasts. Please reference the post in the community section of your replies to find a plastic surgeon in your area