Hey Richmond Neighbor,
Like all our assets, I update estimated values with actual account balances and values at the end of each year. I'm using 4% estimated annual appreciation on our home (Northern Virginia) for the near term future. If you think your area (Richmond) will basically track inflation, you could go with 0% appreciation so that its value is always up to date in real (inflation-adjusted) dollars. So, its value now would be the approximate value in the future, adjusted for inflation. Just include your principal being paid down each year so that you have an idea of your increasing equity over time.
In my calculations, I also subtract out about 9% from the estimated sale price to cover transaction costs when we sell one day (I figure 5% commission and maybe another 4% in closing costs/fees/repairs). That's likely higher than necessary, but I'd rather be pleasantly surprised if they come out lower.
As far as determining the value, I use comparable sales in the area, which are plentiful for us. As a result, Zillow and similar sites also are very reliable tools for determining actual value of our homes.
I don't know about your budget when you retire, but I agree that 30% taxes on 401k withdrawals in the future is very high. Even when I was earning $200k+ my tax rate never approached that high.