Do Androids Dream of Electric Sheep? Questions/Spoilers

Why was the Association trying to keepbounty hunters from working?

Why did Decard start seeing Mercer outside of the empathy box? What was all that "I am permenantly fused with Mercer" stuff?

How did sleeping with one android permenantly frick up Deckards views? He says he loves Rachel. After one or two hours?

Also thought the last showdown was anti-climatic. He walks in there and shoots them with not too much trouble. Sure, he almost died a couple of times that day but except for when he was in the police station, he was in pretty good control of what was happening most of the day.