OK, so you know the saying that to someone holding a hammer, everything looks like a nail? Bear that in mind as you read and ponder my suggestion...
While I think the solo 401(k) idea is worthy, your comment about the ACA subsidy makes me wonder if you're buying your own health insurance. Or at least for some of your family. If that's case, I wonder about the option of using an S corporation for your self-employment income. I say this with some discomfort because as a CPA who does lots of S corp tax returns, I lack some objectivity here... I.e., I am the guy holding the hammer...
But if you buy $10K a year of insurance, you might be able to form a small S corp. You'd maybe need to pay yourself $20K in wages. And those wages would be taxed just like $20K of self-employment income. I.e., you'd pay both income taxes and self-employment taxes/SS & Medicare taxes on them.
But you could with an S corporation put the $10K for health insurance on the S corp's tax return as a deduction (which though a convoluted bookkeeping process would save you both income taxes and self-employment taxes). Your employer pension contribution, in this example would equal 25% of the $20K of wages and 25% of the $10K of healthcare ... so that would equal about $7500 and would again save you both income taxes and self-employment taxes.
A couple of other notes... with this approach you'll have another $12,500 - ish of profit left over inside the S corporation which you could either leave in corp or draw out as a distribution. This may be "unreasonable" in the IRS's opinion... or maybe not. But there are other ways probably to get some of this money out without raising the eyebrows of the IRS.
In any case, you should via this approach save about $4500 a year of payroll taxes. That's pure savings. And you could use that money to make a spousal IRA contribution of probably nearly 6K for your wife. You need to find a local tax accountant who will do the S corp tax returns for a nice low price. But that should be doable.
A question is how you get your savings really up there like you want... But if you have a 403(b) available at your municipal employer, you might be getting pretty close to your objective if you contribute $18K or $24K to the 403(b)... plus your s corp does a $12,500 employer match to a 401(k) or maybe, simpler, a SEP... plus your spousal IRA maybe adds another $6K.
Maybe something to think about...