Oscar, I basically agree with pb4uski but I can add a few things of my own.
When I was planning my ER back in 2007-2008, I split my ER plan into two parts. The first part, which is the part you are concerned about in your question, was getting from my ER age (45 for me at the time; I am 50 now) to age 59.5 which is when I begin to have better access to what I call my "reinforcements" such as unfettered access to my IRA, my frozen company pension, and Social Security.
Like you, I had about $800k overall in my tax-advantaged accounts and my taxable accounts with about 2/3 of it in the former. However, I knew that in order to be able to cover my expenses I needed to change that ratio significantly. I was able to do that by moving 1/3 of it from the tax-advantaged to the taxable, thereby pretty much reversing the ratio to 2/3 in taxable and 1/3 in tax-advantaged. I was able to do this at low income tax rates, too.
I realize that you may not be able to do that as I did but I am also aware of an option called a 72t one can use to withdraw money from an IRA and not get killed on the taxes. I am not familiar with the inner workings of this 72t option but I know others here are (possibly pb4uski?).
As pb4uski wrote, it is likely that your income taxes will be lower in ER than they were while you are working. For me that was surely the case. Besides having income taxed at the highest marginal rate being eliminated first, you may also end up having some or all of your long-term cap gains and qualified dividends taxed at 0%. Between that and my small muni bond fund income, I ended up having only 62% of my income subject to federal income taxes. Remember that you will not be paying any more FICA taxes or commutation expenses, two other nice savings from ER.
Another thing I did in my ER plan was to separate my income taxes into two parts - the "Basic" taxes and the "Excess" taxes. The Basic taxes are those I pay on the normal, predictable investment earnings such as monthly or quarterly dividends from my various taxable mutual funds. These are the ones I build into my ER budget. The Excess taxes are those I would pay on the more erratic and unpredictable investment earnings such as cap gain distributions, especially the rare short-term cap gains distributions which are treated like ordinary dividends. If I receive a lot of these, I know I will have the money to pay for them because it will come out of those earnings in one way or another. In 2010, for example, I had a huge spike in those erratic distributions so while I had a minor cash flow issue (I reinvested them) I knew they would not bust my budget.
I also agree with pb4uski that $48k in annual expenses seems a bit high. Is this for only one person, as you seem to imply, or for a couple? My annual expenses are around half of that (for one person). As pb4uski mentioned, being eligible for Obamacare subsidies will increase a lot if you can get that income lower.