Very nice design Tickle
I agree that he should be 5 life and 5 defense for sure. The
only thing that is missing power wise is an intangibility type power as he can let objects pass through him. However, with his defense and life bumped up to 5 each, I can certainly envision the intangibility as being part of his base stats. Thus blocking more attacks and living long enough to heal often enough will be like him going intangiblish in a sandman kind of way.
Another thing about needing a 5 defense and life. As Tickle mentioned, Spidey can Web Sling Sandman into water. That will lower his defense to 3 for being in water and then down to 1 from Web Slinger and then Spidey will have height for an attack of 5 vs. 1 defense. If Sandman had only 4 life and 4 defense that would be a much easier kill for Spidey and no fun. But at least 5/5 gives him a fighting chance.
Also, at least Sandman can bypass Spidey Senses to try to get a wound on Spidey with Sandstorm.
More maps are going to need sand tiles on them.