When you take money out of an IRA, including a SEP IRA, its all taxed at ordinary income tax rates. You don't account for capital gains, dividends, or any of that- the withdrawals are "simply" ordinary income. There is no capital gains portion of an IRA distribution. If all of your contributions were pretax, then the distribution is all taxed at your ordinary rate.
Many states offer a retirement plan exclusion or deduction, but the federal return will tax the entire $30k.
