Hi J.!
I am so sorry that this has turned in a negative direction for you and your family. Financial struggles are difficult enough, but then to add the mix of a "family" business, it can result in ruining relationships with those you love.
My opinion is to try to calmly speak to your husband about about having talk to your F-I-L. Telling him that he appreciates all that he brought into the business, however, he feels as though he has distanced himself too far away from the decision making process and needs to "reclaim it" to ensure that the success of the business remains. Your F-I-L needs to know that you and your husband want to make sure that if the business begins to struggle, that the blame lays soley on your husband, and elimiantes your F-I-L from any wrong-doing. To me, that sounds like the only way to keep the relationship going between all of you.
In the end, your husband is trying to do the right thing, and most important part in life is the relationships that we have with our families without "business".
My mom and I were business partners for over 20 years. We were successful because we respected eachothers part of the business and was able to seperate business from famliy matters. This was not easy, and I don't think all families can do this.
The phrase "it's just business" should come into play with your husband and Father-In-Law.
Good Luck, J.. I hope your husband can be strong enough, soon enough, to approach your F-I-L.
~N. :O)