The "disease" here is sentimentality for human. Could be why he wasnt too eager on taking back the captured part of his body, knowing full well that the Institute is making human-IPO hybrid with the cell sample. Sort of a Prometheus figure here, so to speak
I think the previous chapter has a translation error.
In this version part of the vampire essence's passive was "Hp exponentially increase" but another translation said "increased health regeneration". Considering how he is fighting during this chapter i think the 2' is the correct passive.
I fear that Thorfinn will be forced to go back to his violent ways. Some people will be happy about that but it's basically like watching a former drug addict going back after he managed to clean himself.