you mention only the gain and social security so I will assume no other income. other income like interest or dividends would substantially alter these figures.
the $500K taxable portion of the home sale will subject 85% of your social security benefits to taxation.
in addition, most of the nonexcludable gain will also be subject to income taxes
assuming that your only taxable income is the $500K capital gain (other income - taxable social security is netted out by your standard or itemized deductions) about $85K is not taxed with the remainder taxed at 15%.
in addition, that gain and your high modified adjusted gross income would also subject MAGI (the capital gain + the taxable portion of social security) reduced by $250K to an additional tax of about 4%
so the total federal taxes would be over $70K
if you had another $25K in ordinary taxable income that would push more of the gain into the 15% bracket and even some into the 20% bracket and more income subject to the NIIT tax and some of that other ordinary income would also get tax at a higher tax bracket. estimate is additional taxes of around $7K
you can do your own calculations using the schedule D tax worksheet. see schedule d instructions page D-16
https://www.irs.gov/pub/irs-pdf/i1040sd.pdf
