Even though you start your ticket purchase by selecting a schedule that does not mean that you are bound to those trains. The SBB will always offer you the cheapest option, and in your case that is the Saver Day Pass. This is good for all public transit in Switzerland, so you can take any train (or tram or bus) in the country. You can change your route, your destination at will.
The trip planner will not propose impossible transfers. What may appear “short” to you is just normal. But if a delayed train cause you to miss a connection you just take the next one. And that you can do with any ticket, even a Supersaver ticket that is tied to a particular departure.
If you bought your Saver Day Pass with HFC reduction you will be requested by the conductor to show it. You do not need to “combine” anything. Just show both the Saver Day Pass, and the Half Fare Card.