Ariespiscescusp...i would very much be cautious about any man (no matter what the sign) that after a few weeks is so anxious to speed things along. Especially if you are feeling somewhat threatened by that intimate invasion chuckles. I know I would raise an eyebrow to talk of moving after only three weeks. Wait until after your first fight and see how it goes That is always telling
As far as Cancers...indeed they are sensitive. I have never dated one in my life until now. Here are my observations. Mine was observant and cautious and guarded at first. The tough shell...hard to break through. Very much the hot and cold you speak of. It drove me insane! But in time with good talks and being open about life and having some adventures and road trips, that shell dissolved to expose a very sensitive man indeed. I am shocked sometimes at how wonderful that can be to see a man not be afraid to be so happy they have tears running down their faces.
I would not call him possessive in any way compared to say, leos, and he loves the simple things in life. Snuggling on couches, holding hands, just being together. He is not high maintenance and very focused on comfort and having a good time.
I can really see the up and down/hot and cold side of which you speak though. But I have seen that with many men LOL. I think in the case of cancers...when they are doing that, they are questioning even their own motivations in the relationship and thus their tendency to hide back into their shells and need space. Women have to learn to give them that space and take that space for themselves too. I myself need space.
However, Taurus and Cancers work very well together I know. I could see how a Cancer would drive the typical Aries crazy. My best friend in college...she was an Aries. We were greatest of friends and rarely ever fought but I have never even encountered an Aries man!!
As far as having a "I won't date a...." I can say that I would not date a Leo again mainly becuase a Taurus and Leo man are like two 5 year olds when we fight...both wanting our own way and butting heads and never finding common ground. I have lived that and honestly every Leo I know is the same. NOt in a bad way at ALL, just that as partners they are better off friends and not lovers imho!
Best of luck to you...just be true to yourself and your needs first and foremost. That is not selfish to determine at this point. If its not what you want, respect your needs, and do what is best. But Cancers are sensitive and loving and sweet and very affectionate. Mine is the opposite of selfish...so it does exist.