From everything I have read AND observed I would say yes, INFJ males are very rare. How rare is a matter of debate. And rare does not immediately mean "special" or "awesome"...just rare. I have only met a couple other guys in my life I am sure were INFJ's. I've always felt I was pretty different from most guys. This shows and has caused me to be labeled "gay" for much of my younger life. I've grown a lot in confidence and wisdom since then and don't seem to get that anymore.
I think INFJ to INFJ is and would be a great combination. I happen to know an INFJ/INTJ female and we...well it's a good combo. One thing I think I can say about INFJ males (probably females too) is that we tend to do things slowly and carefully. We thus change and grow a lot, later in life then many other types. If you are set on an INFJ male, I would suggest looking for one a bit older then you normally would if you are so inclined.
INFJ males are extremely affectionate (and loyal) once they are comfortable with you. The time this may take varies according to individual and ...again...age. "E" types without a doubt can get comfy more quickly. For me, physical touch is my primary "Love Language" so I love to hug, hold, and touch. From what I've seen here, INFJ's tend toward this love language as well as "Words of Affirmation", which again makes sense since we are a very (written) word-oriented type. Expect an INFJ boyfriend to write you lots of nice letters or at least be able to articulate his love if that happens.
IMO we really don't start hitting our stride, where our stronger postitive traits shine, until 30 or so. It was even later for me...more like 35. This is based purely on my own observations and my everpresent Ni. A fully realized INFJ is a great thing to behold (though I suppose you can say that about almost any type!).
All of this is observation and research on my type. It's not set in stone. It's not scientific fact. Typology is not an exact science. Individual INFJ's will vary. You can really only say what one of us is more likely to do or be like...no absolutes. Good luck!