I accept Finnur Jónsson's syntax here, although my interpretation of the meaning differs slightly:

Ne djúp-akörn dólgs drápu stall firum, stríðkviðjundum vamms, við falli rastar Glamma stöðvar, i.e. "the deep-acorns of hostility [hearts] of the men, who firmly oppose disgrace, did not miss a beat at the surge of the current of Glammi's haunt [ocean]".

djúp-akörn dólgs ] "the deep-acorns of hostility" is a perfectly normal kenning for "hearts". Cp. þróttar steinn "courage-stone" in 10:8. The use of the words djúp "deep" and dólg "hostility" are hardly coincidental, as Thor is wading the deep, which is hostile to him. Cp. háðu stáli stríða strauma in the previous stanza.

drápu stall ] The origin of the expression drepa stall is not known, but its meaning is well attested to. The subject is always hjarta "heart", and hjarta drap stall means "the heart stopped", or "the heart trembled", or, perhaps, "the heart missed a beat". All occurences of this expression express a feeling of fear.

stríðkviðjundum vamms ] The meaning of the obsolete verb kviðja is "deny, obstruct, ban". Vamm means "evil, disgrace, wickedness". The prefix stríð- was (and is) commonly used to intensify the meaning of a word, "strictly, firmly, greatly". Thus stríðkviðjendur vamms are those who firmly oppose evil and wickedness, i.e. Æsir, here Thor and Þjálfi.

falli rastar Glamma stöðvar ] Glammi is the name of a "sea-king", and his stöð is the ocean. Cp. the similar kennings: Glamma skeið, Glamma slóð, Glamma þjóðtröð, which all mean the same. Thor's (and Þjálfi's) blameless heart doesn't miss a beat, when the "fall of the current of Glammi's haunt" threatens him.

Sveinbjörn Egilsson read:

Ne akörn dólgs drápu stall firum, stríðkviðjundum glamma stöðvar váms, við falli djúprastar.

It is, of course, possible to take djúp with either falli or rastar, but the tmesis is better avoided. Egilsson (and subsequent commentators) understood glammi as a heiti for "wolf", which is quite possible. Thus, glamma stöð becomes a mountain. In vams, Egilsson saw the word vámur "loathsome creature; monster", and via a dubious interpretation of stríðkviðjandi as "enemy, one who makes war", he arrived at the kenning stríðkviðjendur glamma stöðvar váms, i.e. "those who make war against the monster of the wolf's haunt".

As mentioned above, my reading of the syntax is basically identical to Finnur Jónsson's. He, however, reads djúpfalli rastar glamma stöðvar "the deep current of the wave of the mountain", guided by Snorri's statement that Thor is wading a mountain river, rather than the ocean.