Si la sospecha está por encima del 20 o 30 % no te deja subir el afecto, pues por obvias razones sospecha de ti, pero puedes reducir la sospecha o al menos no aumentarla si regresas todo a su lugar en la noche, o sea que la vistas de nuevo y la cubras con su manta.
Yes and no, relationship stays on 20 and then later on 40, as Yuna expects you to do something specific for her (your character says something like "I feel like my relationship isn't progressing, I need to talk with her about it" which is a hint for you to go to her at night and chat with her (living room -> give gift -> chat) she will tell you what you need to do in order to progress)
Suspicion also plays an important role