With all due respect, why are black holes so wild and illogical? By everyone's disgruntled reactions, I can only guess that when everyone saw a pinkish-purple rocket launcher send people 10 years into the future, they flipped a sh*t! Has anyone even watched the science channel? Michio Kaku is boss. He explains in some special that it's possible to escape black holes...damn...earth shattering (get the pun?) facts! The point is, staying on the edge of a black hole with a certain acceleration can allow a body to escape the hole's pull. Furthermore, these are mini black holes, the size of which are millions of times smaller than real black holes; their small size means that not everything is bound to be sucked in: as long as light and mass are a certain distance away, they will not suffer a twisted fate. Plus, small black holes are quite feasible; however, they collapse quite easily.
Now, as for Enma's ability to will black holes into existence, this is quite plausible also. Enma's earth flame allows him to manipulate gravity, much in the same way that Tsuna's sky flame allows him to petrify things and boost up to phenomenal speeds. The fact remains that upon the seventh day, after spilling the Sin on the Simon rings, the earth flames would increase 7-fold in power. To over power Tsuna's awakened Vongola ring with just the base power up, why is it not reasonable that a full-blown power up would lead to such profound strength in order to punch holes in the fabric of space-time? The real kick will be when Tsuna matches Enma's powers and is able to boost right out of the black hole's stranglehold. That's exciting.