AdamObomb
Adam: If you have not done so, I strongly suggest you get an attorney; preferably one with products liability experience. I do not know anything about the law of your state, but individual states that law suits be filed within so much time of an injury. For exmple, one web site from an Indiana attorney says it is 2 years for a personal injury case, but to verify the period of limitations of actions with an attorney.
There are also rules specifying the tolling of the period, which I won't get into but even if one's period seems to have expired it may have time left should one or more of the tolling rules apply to their situration.
Depending on your states laws, there may be no such thing as a "freak accident" if this is classified as what is called an "ultrahazardous" product. If it is and if you were using the product in the manner for which it was intended, and it sounds as if you were doing just that, you may have a very strong case. In some states, and I don't know the law of your state, a manufacturer is held "strictly liable" regardless of negligence, for injury to a consumer as long as the product is being used as intended.
I don't know about the manufacturer of your gun, as you modified it and had it since you were 10, but an attorney from your state can advise you on that. I am focusing on the 209 conversion kit and possible more than its manufacturer.
Once again, depending on the law of your state, anyone involved with the "stream of commerce" of the kit may be liable. The manufacturer, the importer, distributor, and retailer. I assume you installed it yourself according to its instructions.
You may find this article helpful. even if your case has nothing to do with CVA. I suspect its author may be able to refer you to an attorney with expertise in black powder cases.
http://www.chuckhawks.com/dangerous_muzzleloaders.htm
I hope your recovery is going well. Please find an attorney as you should not rely on anyting I have written as it may not apply to the laws of your state. In fact, if the conversion kit was purchased in antother state or hour injury occured there, your state's laws may not even govern. Get an attorney.