Too many things here already for you to respond to. In general I completely understand your point of view. In fact.....I once shared it. Not only did I see the distinction, but because in general I had great relationships, and loved the people in the hall, I thought I would stay for the sake of them, and the good that exists.
I agree that good exists as well. None of us is 100% good or 100% bad. We are percentages of both, all the time.
But here is why I could no longer go. I'll try to consolidate the two ideas.
1) You say Christ has a command to preach, but when you do so associated with the WTBTS, you direct them to that organization. You may think you are not, but you are. Or is your intent not to baptize them? why not just engage in a personal ministry as you see fit? You do not. You take place and therefore represent, the group with whom you disagree.
2) Blood. This is an incorrect doctrine. thoroughly debunked. If you "witness" to someone, they become a JW, you disagree with this doctrine but you have helped them into an organization where other factors come into play......are you bloodguilty if they or their children die as a result of this stand? It may be an extreme example, but what culpability would I have as a person who directed someone to do something that I personally did not agree with?
Your conscience is telling you something. Its why you are here. I'm not certain what you feel they have "right" vs "wrong". Maybe that is a good place to start the conversation.
Its not all bad. But are you tainting your worship to your God by not being authentic? I felt inauthentic, and therefore refused to support the GB in any ancillary way.