2. You did not tell us any contract contingency. If there is any contigency, you simply backout that the contingency does not meet. You do not have to mention the railroad at all. If there is inspection contingency, fix or not fix does not matter.
3. If there is HOA, you have more option to back out, simply tell them that you do not like the HOA bylaws.
4. Be firm, be patient, and you will get your deposit back. If the seller does not return the deposit, go to the court. The seller will not be able to sell the house if the contract still bind both of you and the seller has to pay mortgage during that period. If you close the house, the burden is on your shoulder.
Again, do not close, be strong and firm. Listen to your heart and do not buy a house you do not like.
Good luck. I write in hurry and did not check grammar or spelling. Sorry