OK, your husband being an employee make things a bit different. Normally if the business has employees, the business can't have a solo 401(k) plan. What follows assumes that that restriction does not apply if the employee is the owner's spouse, but that might be a bad assumption. It's possible, perhaps likely, that the fact that the employee is your spouse is not relevant in determining whether the plan must meet the requirements of ERISA; solo 401(k) plans do not meet the requirements of ERISA.
Your husband's contributions are based on his compensation reported on the W-2, with elective deferrals being deducted from his pay. If you are making the maximum permissible employer contribution, that would be equal to 25% of his compensation. His wages and the employer contribution made for him are expenses of the business reportable on your Schedule C.
Your maximum contribution would then be calculated roughly as I described. Your net income would be your net profit minus the deductible portion of self-employment taxes and your maximum employer contribution would be 20% of that because 20% is the self-employed adjusted rate for a 25% base rate.
Because the employer contributions must be determined from that same base rate, it's almost certain that the employer contribution for your husband will be different than the employer contribution for you. Making them come out equal is virtually impossible, particularly since your husbands wages were determined several months ago as a W-2 employee of your business. The only way for them to come out equal would be if you each had enough income from the business to support the maximum possible $43,500 employer contribution (when each makes a $22,500 elective deferral). That would mean that your husband's compensation from your business would have to be at least $174,000 and your own net earnings from the business would have to be at least $217,500, double what you say the gross income of the business was.
Since you both have other jobs, any amount than an individual defers to another employer's qualified retirement plan (other than a 457(b)) reduces the amount that that individual is eligible to defer to the solo 401(k). TurboTax does not enforce this limitation, you have to do that yourself.
"my spouse would be included as a W-2 employee"
That's an odd turn of phrase. It seems to suggest that you have not paid your husband timely and issued your husband a W-2 timely as required by law. If you haven't paid your husband, it seems that your husband is actually a 50% owner, not an employee. Treating your husband a 50% owner of the business means that my original reply applies and eliminates the ERISA concern.
