Can your balls explode from too much sex?

As far as I know, I don't think so...the testicles don't work under muscular power the same way that your heart or your intestines or your orgasm muscles(bulbospongiOSus) do, they simply generate some of the elements needed to procreate life(among other things) so there's not really any chance of "over-working" them, in that sense(ie: having a "ball-attack" like a "heart-attack").

It might be possible to sustain an injury or some type of abrasion, trauma, etc. during any type of sex, however, no matter how much or how often or how frequent or how vigourous, etc. which might lead to situations similar to what you're inquiring about...otherwise, I should think no worries.

No, but they can deflate from over-use. This is not a serious condition. It may be uncomfortable for a while but it is self-correcting within a day.