Irregular past tense confusion with compound noun/verb. More examples? [closed]
Here's an example of the neologism on-lend (give a loan with money lent from other companies)...
...central bank credit was a major source of finance for banks (on-lended at fixed spreads)...
...which illustrates the general principle that verb nelogisms are normally regular. The established pattern over centuries is that irregular verbs are disappearing; so long as the nelogism is genuinely perceived as a "new" verb (as it probably is with breakfall, on-lend), it's automatically treated as a regular verb by default. So just use breakfalled.
EDIT: I should point out there's no definitive authority specifying how any given verb neologism will be conjugated before usage becomes established custom and practice. For example...
Google Books favours troubleshot over troubleshooted by about 7:1. But on Google Internet (which I assume represents more widespread current usage), the bias is only half that. My guess is that as people get more used to troubleshoot as an "independent" verb, they'll increasingly regularise it.
But all "authorities" now seem to agree that for the baseball (ex-)neologism to fly out (to hit a fly ball), the "correct" past tense is flied out (not flew out).
My suggestion for OP to use the regular form is partly based on the fact that I have absolutely no idea what breakfalling is, so I make no close connection between the neologism and the component (verbs?) break and fall. And either or both could be seen as "nouns", which would make me even less inclined to replicate the irregular verb forms.
Inflection will mask.
From a simple plain-English speaker's perspective, verb neologisms necessarily need to have regular conjugations so the neologism could be visible.
Among breakfalled, breakfell, brokefall, and brokefell, only breakfalled contains the neologism in toto.
Related verb, fell ("make fall, cause to fall,") pt. felled.