To take away our sins. He takes them away by forgiving those that have been committed, by helping so that they are not committed, by leading to life so that they cannot be committed at all.
Ducendo ad vitam makes sense, but there's something weird
here because the abbreviation isn't the usual one. Normally it would be
vita with a macron above the "a", and here we have
vitaz... Which would make no sense as an abbreviation of
vitam, seeing that the latter doesn't have more letters. Maybe just a typo... Dunno.
Whosoever abides in him. As if (someone asked), "And what use is it to us that he has come without sin?" Response: Whosoever abides in him, sins not.
Matthaeus, the parts in italics at the beginning of each gloss are fragments of verses, so you should not try to translate them as if they were complete sentences by themselves; just look at both bibles and pick the corresponding English fragments. Besides, reading the verses is important to grasp the context, and so to translate correctly: here for example, without knowing the context it could indeed have been "in it"; but if you read the verses you know it's "in him".