According to DNA Painter, 1673 cM is a half-sibling relationship, which you seem certain about anyway. All other relationships described fall within the shared cM range for 1st cousins (396 - 1397), including 1056 cM, which is what I think the amount shared between your half-sister and Cousin #1 is (not clear from original post). 994 cM is also well within the range for 1st cousins, and precludes any half-sibling relationship between yourself and Cousin #1.

Your other maternal cousins in the 700-800 shared cM range with yourself are still more likely to be whole 1st cousins, but half 1st cousin relationships cannot be ruled out.

According to DNA Painter, 1673 cM is a half-sibling relationship, which you seem certain about anyway. All other relationships described fall within the shared cM range for 1st cousins (396 - 1397), including 1056 cM, which is what I think the amount shared between your half-sister and Cousin #1 is (not clear from original post). 994 cM is also well within the range for 1st cousins, and both preclude any half-sibling relationship between yourself or your half-sister and Cousin #1 (or #2? - again not clear from your post). You are all 'just' cousins.

Your other maternal cousins in the 700-800 shared cM range with yourself are still more likely to be whole 1st cousins, but half 1st cousin relationships cannot be ruled out.