Each skycraper at it's largest dimension is 27*27 blocks. Lets assume all skyscrapers from henceforth are stright edge 27*27.
That means per meter, you have a minimum of 107 blocks.
Now, the y= value for the enterance to this typical skyscraper included in this evaluation is 51. This skyscraper's roof starts at 214. Assuming the skyscraper is perfectly square all the way up to here with a blank floor every 7 meters, this means you would be having to remove approximately 31600 blocks PER SKYSCRAPER.
This is of course assuming the skyscraper meets these perfect requirements. However, not all skyscrapers will be the same. Some are shorter, some are taller. Some are built out of glass and quartz, some built out of glass and hardened clay. Point is, to destroy a small town consisting of more than 2 skyscrapers, you'd have to be online for a very long time to destroy just the two. As tnt is hard to come by, unless you've been duping some in, which I doubt you would, as someone who is posting "anonymously" on the forums would be aware that their IP is logged every time they view the forums, and as a result would know that they would be global banned as a result of doing this, I'd say you have little to no chance of ever being able to destroy a single skyscraper. Maybe a few of the smaller houses, yes, but an entire skyscraper would be madness.
TL;DR VCR repair man is NOT Tyler Durden. Project Mayhem is a no-go referral scenario.