You can make both a SEP-IRA contribution and, as long as you were under age 70½ in 2018, a regular traditional RA contribution. Neither of these can reduce your taxable income below zero and neither of these can reduce self-employment or other "Other" taxes on Schedule 4. You cannot avoid paying self-employment taxes on the income from self-employment.
With relatively low AGI and taxable income, it might make sense to make your regular IRA contribution to a Roth IRA instead of to a traditional IRA, particularly if your taxable income is already zero without a traditional IRA contribution. There is no age limit to making a Roth IRA contribution, only a modified AGI limit.