Let me be clear. You are the DM, you have final say. There are several courses of action available to you:
You can confront him. "Hey man, you're being really pushy, forcing me into decisions and I don't appreciate it, and neither do any of the other players. A lot of your ideas aren't what I want to do with the game. Everybody's ideas will be given fair consideration but as the DM, I have final say. Please stop being so pushy. If you continue, you will be removed from the group."
You can straight up kick him out of the group. If the rest of the group agrees with you, as you said, then they should support this decision. "Alright look man, you're being a real jerk here and we don't appreciate it. You are no longer welcome to our D&D sessions."
You can talk with the other players and see what they want to do. "Hey guys, you all know this guy is being a bit of a bully to me and I don't know what to do. I don't want this to continue because he's making me do things with the game that I don't want to. What do you think we should do about it?"
You can offer an ultimatum: "Alright guys, look. X is being a real jerk to me and it's driving me crazy. I hate how he treats me and I can't handle it. Either X has to change their ways/leave the group, or I'm going to leave. I'm not going to be treated like a doormat."
You can continue and simply ignore the suggestions that you don't like, and respond with "I don't like that idea, we aren't doing that. End of story, if you continue to pester, bug, or harass me you will be removed from the group."
In my opinion, your best option is to say "What do I want? As the DM, do I think he's capable of changing his ways? Do I just want him gone? What do I want to happen?"
- Talk with him about the problem and see if he's willing to change.
- If he isn't willing to change, talk to the rest of the group about potentially removing him from the group, or finding some other solution.
A lot of the time, the problem can be solved by just talking with the person and hashing it out. Explain how you're feeling and what you'd like them to stop doing, and let them do the same. You may discover they are very willing to change, or you may discover that they are not compatible with your group and the best course of action is for them to leave.
You shouldn't have to deal with bullies in your downtime. You should be having fun, enjoying the game with friends.
Realize one very important thing:
YOU ARE THE GAME MASTER!!
You are the ultimate authority in this gaming group, you have final say on anything and everything. If you have the support of the rest of the group, you can pretty much do whatever you want to fix the issue you're having with this player.
Personally, I would remove him from the group, let him know he's no longer welcome to participate in your games, and be done with it.
If he's a friend of yours, your best course of action is to confront him, tell him what he's doing that's wrong, tell him why it's wrong, tell him what needs to change, and tell him what's going to happen if he doesn't change.
At the end of the day, no matter what you do, don't avoid the problem. You can't fix a problem by ignoring it and hoping it eventually goes away,