'iipach: This is the standard word for "man" in some non-'Iipay varieties, and considered slang in other dialects. The -ch here is part of the word, not a suffix. Similar to 'iipa, the most common word for "man" in Tiipay, also used by Robertson.
wewuuw: This is a variant of the word ewuuw, "sees, looks at (it)". In other instances, Robertson appears to say ewuuw for the third-person singular. 'Iipay plural is ewup, however Robertson uses the Tiipay plural uuwich.
Assuming 'iipach is the subject, this sentence is, "A man sees/saw it." Based on context, unmarked 'iipach could also be the object of wewuuw, making this sentence, "He saw a man."