I’m trying to wrap my head around the income statement and the balance...

As you say, unlike the prospectus/summary prospectus, the Statement of Additional Information shows the fund’s income statement and its balance sheet. An open-end fund is a large portfolio of securities. Bonds generate regular interest payments to the fund. Many common stocks generate regular dividend payments.  That represents the portfolio’s gross income. Next, operating expenses are deducted: management fee, transfer agent fees, custodial fees, etc. What is left is the net investment income, and most of this is distributed as dividend payments to the shareholders on a schedule established by the Board of Directors. The balance sheet shows the assets of the fund—the portfolio securities. Against that, the fund may have some liabilities—perhaps they borrow money to pay out redemptions to shareholders. The difference between the assets and liabilities equals the net assets of the fund.