Mar 11, 2015 - 3:32 PM
Tickets within Switzerland have a fixed price, so you can just check ticket prices for any date. It won't be different in May. Tickets in and to/from other countries may get more expensive when the date gets nearer. Also they often require seat reservations. You need to book a ticket from Gengenbach to the first station where your Swiss Half Fare Card is valid (Basel or Schaffhausen, depending on the route). There, you can purchase a 50% discounted ticket for the Swiss portion of the trip.
For Lugano to Verona, you need a regular ticket from Chiasso to Verona. And you can get a 50% discounted ticket for Lugano to Chiasso.
I don't know about discounts in Germany for seniors, but if you split the tickets in two sections as explained above you can get that discount on the German leg.
There are several resellers where you can buy the Swiss Half Fare Card, the ticket for Germany, and the ticket for Italy, all in one go. In your case, being a US citizen, www.raileurope.com would be a good choice. Please find all resellers here:
I'm not sure I understand your last question, but the start date on the Swiss Half Fare Card should be the day you reach Switzerland.
We just posted a video on the Swiss Half Fare Card page, perhaps that helps you out as well.