I am a pro at expressing myself to an ISTJ that has a HORRIBLE time reacting and expressing.
Presentation is everything.
I never question him...or try to corner him.
It goes something like this and my situation is far more involved but similar in structure:
"I want to give you some information as to how I feel, and need you to understand I have no expectations. If your situation ever changes and you show up at my door....I am never letting you go. I mean that...."
Then I generally have to lighten things up or we both will have a meltdown:
"And anyhow, I have duct tape and a cage......that will make it especially difficult for you to escape."
Then we dont talk for a week.
**If it helps, he has told me on more than one occasion that I am the only one he has ever encountered in his lifetime that truly GETS him. He has even said at one point he understood what people meant by 'soulmate' after having me in his life. Once he laughed and said that we were separated at birth.
If you truly want to communicate, you have to understand how he is going to perceive what you put out there...and that means trying to understand his perspective.