As a shareholder in an S corporation, you are not self employed. Social Security and Medicare taxes are withheld from your pay reported on your W-2. Your SEP-IRA contribution is also not reportable on your personal tax return because your SEP IRA contribution is made by the S corporation based on your W-2-reported income and deducted as an expense on the S corporation's income tax return.
There is no reason for these to appear on your Schedule K-1 (Form 1120S). Your Social Security and Medicare withholding are reported on your W-2. Your SEP-IRA contribution might also be shown on your W-2, but only for your information, not for reporting anywhere on your personal tax return.
The IRA custodian should mail a form 5498 showing the contribution ... these usually show up in May of the following year.
