“will be a house of God.” That is, a place of worship. True to his word, many years later Jacob did build an altar to God at Bethel (Gen. 35:1-7). Jacob would have sacrificed on the altar even though the text does not specifically say so, because sacrifice was what altars were built for.
“a tenth, yes, a tenth.” This is the figure of speech polyptoton, which occurs when the same word occurs in succession in a sentence but the word is inflected in different ways. For information on the figure polyptoton and the style of translating it, see commentary on Genesis 2:12, “eat, yes, eat”].