TL;DR - I inherited an asset, but I'd like to see if we can retire without it, at age 62-65 or so

I've run a bunch of online calculators such as firecalc and AARP, but would also like feedback from people who are closer to pulling the trigger on retirement and have a better understanding of the calculations. I'll represent my numbers in terms of "x" being annual spending.

Here's the scenario not including this inheritance

Me: 42, spouse: 42, legally married filing jointly, 25% tax bracket

x = annual spending in retirement*

4x = total retirement savings so far**

x times 40% = new annual contributions to tax-advantaged retirement accounts

*I arrived at "x" by taking exactly what we spend now from our net pay, and subtracting our Roth contribs. (In addition to taxes withheld from gross pay, we usually owe the IRS about $1000/year, which is included in the retirement budget.) We have a mortgage of P&I = $900, and that will be paid off by retirement, but I left it in the retirement budget to account for any future health expenses.

**The retirement portfolio = index funds at 75/25 stocks/bonds, with a weighted expense ratio of 0.07%. The accounts are 40% Roth and 60% non-Roth, but all are tax-advantaged.

We're both eligible for social security, i.e., we're not public school teachers. I will also have a small non-COLA'd pension of a few hundred a month, but I always leave this out of the online calculators. We have no children.

We seem to be on pace, but online calculators make different (or no) assumptions about taxes and SS, and this can be confusing.

Here's details

Conveniently for our math, the inherited asset is worth "x"; is not liquid, but could be sold. It's an artifact that will appreciate at the rate of inflation and I'm familiar with the marketplace for it. Because reasons, we wouldn't part with this unless we were already eating cat food. We would like to leave it to charity upon our demise, but want to make sure we'll be ok without it.

(Legally, the inheritance is mine, but my spouse wants to be included in the plans, and I respect his feelings.)

Thanks!