Wow. The large block of text makes reading your post difficult. In the future, you may want to either use bullet points or just get to the point a little faster.
1. Your agent has to work with the seller's agent. If your agent is getting no response, they can contact the agent's broker. If still no response, they can go to the local board of realtors (if they are a REALTORŪ), or to the real estate commission.
2. Sounds like you are dealing with an unmotivated seller. Not sure why they'd wait for the other buyer with a good offer on the table. The seller' agent should do a better job of advising them.
3. I always include an expiration in my contract. The wording is that the contract is voidable if the seller does not respond before x date. Sounds like your agent didn't do that.
You may have your agent send an addendum that gives an expiration to your offer. You should also move on to another property.