i suggest you contact other HAVC companies to determine a solution to your problem. We use KRAFFT and have for 18 years. My neighbors use ARC. Humidity in a home can come from a series of issues and while I can sell real estate, am not qualified to provide you HVAC solutions. That takes a qualified, liscensed and insured vendor.
I agree with most in that removing the fp may not be a good thing. Most people will value the fireplace and most appraisers will give it 3-5k at least. I have 3 fireplaces in my own home..2 of which I never use..but I still would not get rid of any. The age of your home factors in quite a bit with the importance of the fp. I suspect your home is older since the closet space is not as great. I believe the previous posts..should validate your question.
Most likely the removal of your fireplace would only be validated if the cost of repair exceeded to cost to replace.