vivos voco. mortuos plango. fulgura frango
I summon the living, I cry for the dead, I break lightnings [pl.].
The vivos voco engraving on the the Schiller Bell. Source: Wikimedia Foundation
Wait, the first two feats a church bell does indeed, but breaking ligtnings???
Yes, and the source of the first part of the inscription cited in the question is quite unambiguous. It harks back to the practice of Wetterläuten, or weather ringing, a belief that ringing a consecrated church bell would repeal an approaching storm, associated with the demonic, evil forces. Perhaps the most known and one of the earliest is the 4.5 ton bell of Schaffhausen commissioned in 1486, also called the Schiller Bell since Friedrich Schiller used the full text of the spell as the epigraph to his Das Lied von der Glocke, to which Goethe added an epilogue to be read at the Schiller's funeral. In fact, this inscription is quite common on church bells across Europe, from Germany to Spain.
It is worth noting that the belief not merely existed among the common superstitious folk, but was also condoned, if not espoused, by the clergy. The Schiller Bell was indeed commissioned by the abbey! Whether he did that out of his own belief in Wetterläuten, or to placate the flock, I do not know, but I would not be much surprised if the former was in fact true.
Also semantically and pragmatically notable is the Medieval use of fulgur as the culmination of bad weather, brought up by evil forces. For a Roman, such a disrespect toward the lightning would be perceived as a hubris, a sacrilege; fulgur to them was an act of Zeus personally present, an awe-inspiring and deadly appearance of the Olympian in the mortal's world. For the Roman, a place struck by lighting was a sacred one, fulgur conditum (lit. “here lies the lightning,” as if buried), chosen by lightning, implying Zeus himself. For the Christian, in contrast, it was an act of the forces of Evil.
I jest with (=by using) feet
This paraphrase of the vivos voco spell does not make much sense out of context. The Latin reads clearly: the speaker makes jests by using feet. Since Latin, unlike English, does not express definiteness grammatically, it is not possible to tell whether the jests are performed using one's own feet (“the feet”) or some indefinite feet.
Another meaning of pes is a poetic meter, also expressed in English and many other languages, which is unsurprising since the word for “foot” also served as the unit of length in multiple cultures and therefore languages (Latin not being an exception).
The final syllable rhyme is entirely alien to classical poetry, but common in Medieval European verse.
So any possible reading does not make any sense outside of the cultural context. My best guess is that this is a clumsy translation of some local idiom, close in the meaning to “jesting with [one's?] feet (<extremities)” or “joking with a [poetic] meter.” Note that the latter reading would impart a self-referential meaning to the whole verse; this is not, however, an argument for preferring it, let me repeat myself, not knowing the proximate cultural context.