Here we have a typo in the 1841 edition that is marginally possible; instead of the know of the original text (“I have heard and also know”), the 1841 edition reads “I have heard and also known”. The 1841 typesetter may have been influenced by the expected phraseology from “have heard and seen”, where both verbs are past participles, as in the nearby example in Jacob 7:12: “for I have heard and seen”. Of course, the use of the present-tense know is more appropriate since Sherem’s knowledge of Jacob’s preaching is continuous and is not complete.
Summary: Maintain the original present-tense know in Jacob 7:6 (“I have heard and also know”).