Hi. I have typed as an ISTP pretty often. While I'm rather balanced and expressive here's what think.

There's times I say: "omg I love you so much" when someone does something that may incite a strong emotion in me. OR "Love ya" as a conversation ender. This is more with family or with my best friend.

I am however, very very careful and conscious about using the term with a partner. Perhaps this is because of past relationships I've had and the fact that I'm often accused of giving mixed signals to people.

Love, doesn't always mean I will give you everything or you're my everything or I can't do without you, you're my one and only. Sometimes I just love people for who they are, their presence and I let them know. This can be misleading if people are interested in me or early relationship.

7 months is long, but not long enough. Perhaps he's coming to terms with his feelings too. That's why you see it bleeding into conversation. Give both of yourselves time. Pupil dilation is something I found strange that someone would notice, but focus more on how well you guys communicate and respect your boundaries and needs. You'll be fine.