Ahh your vacation sounds like the life!
I would go with Mesillas Yisharim for mussar too, i learned it maybe four times with different people and still learning it now in a chabura and then doing chazarah with a friend. Each time you read even the same passage depending on your stage in life you gain something else! Its the classic mussar sefer, like thats where you start.
Both Alieh Shur and Nesisvos Sholom are great and i can go on and on about both. Another sefer i would teally reccomend in this category would be any by Rav Pincus. Nefesh Shimshon on Emunah Bitachon, or Tefilla- it will literarly transform your Davening. Or shabbos malkusa which i learn with a teacher- shabbos is something most us of keep all our lives but makes each one special? You cant imagine how much there is to the hashkafa aspect of Shabbos! And if you learn it during the week every time you are mikaim the mitzva of preparing for Shabbos!
And about Emunos ViDayos (by Rav Saadiah Gaon?) i know its not readily abailable in a general sforim store as i looked into buying it last year and couldnt find it. I was explained that nowadays most hashkafa sforim are based off of that so yeah….
And modern day teshuvos sorry im not a guy so cant help you there 🙂