Question 1: I don't have an income right now (working on that), so I can't contribute to any kind of retirement plan, correct?
Not exactly. If you file jointly, you should be able to contribute to your own IRA in your name. When you file jointly, the IRS is looking at your joint income, so because your husband has income, they consider you to have income. You can do Traditional or Roth.
Question 2: Does it make sense to get some other kind of retirement account for any money that we want to save over the $150/month? Or just stick what we've got into the SIMPLE IRA?
No, if you're talking about a Traditional IRA. They do the exact same thing, which is reduce your taxable income. So putting $1,000 into a SIMPLE does the same thing to your taxes as putting $500 in a SIMPLE and $500 in a Traditional IRA. Either way, it's $1,000 of a tax deduction. If you want to put it into a Roth, then that's a different story, depending on what you are trying to achieve.
The tax deduction things are confusing me. It looks to me like any money we put into the SIMPLE IRA isn't taxed. Is that correct?
Yes, it's tax deferred. Which means the amount that your husband puts into the SIMPLE is reduced from his taxable income as a deduction. He pays taxes on it when he pulls the money out as a taxable distribution.
My dad was able to switch his over to a vanguard SIMPLE IRA.
Sidenote: be very careful about this if the SIMPLE IRA is relatively new. SIMPLE IRAs aren't really that "simple." There is a unique rule that applies to this type of account. You cannot transfer a SIMPLE IRA within two years of the first contribution without receiving a 25% penalty. Likewise, the 25% penalty replaces the 10% early withdrawal penalty if you redeem assets before that two year mark. So, if you husband started CONTRIBUTING within the past two years, consider leave it parked in the SIMPLE.
Hope this helps.