I don't think you're being unreasonable. This is your first house and the biggest asset you are likely to have for a long time. Now, I don't know much about how this is all done in the US, as it's a little different here- but the concepts are the same.
Your agent should be working for you. You hired them, you're paying them. Make sure you are happy with the service they are providing.
If you want to get any sort of inspections done, do them. Don't let anyone put you off doing them, telling you it's not necessary. I just bought my first home myself, and got a building report done- and thank god I did, as the firewall needed replacing. This knowledge left me in a good position to go back and negotiate, even after the contract was signed.
As for the value, go with your gut feelings. Negotiate as you feel appropriate, do your research on the market, and don't be afraid to walk away if they won't negotiate with you. As someone else said, just because the vendor spent X amount of dollars improving the property, doesn't mean they increased the property value by X amount. To me that sounds very out of proportion to the actual value of the house