How to make the best use of Eurail pass?

Hi everyone. I will go to Switzerland in early June but many things are still unsettled.:((
I've bought a Eurail selective pass(7days) and I'm now wondering if I should buy a Swiss half card or other pass since many people said Eurail pass is not that useful in Switzerland.
My plan is as follows:
Day1:Pais-->Bern(half day)--> Grindelwald (use Eurail Pass)
Day2: whole day in Grindelwald
Day3: Interlaken(half day)-->Lugern, a small village, to sleep in farms
Day4:Lugern
Day5:Lugern-->Luzern-->Mt. Titlis-->Luzern
Day6:stay in Luzern and set off to Germany at night (use Eurail pass)

I will also use the Eurail pass for another two times in other countries so that means I can have 3 more travelling days to use it in Switerland. How can I the best use of it? Can I use it on day 3?
Actually, what is the total fare from Luzern to Mt Titlis? How can I go to Lugern from Interlaken and Luzern from Lugern?

Thank you a lot!!:-)