I don't think it's possible to give a definitive answer as to whether you would qualify for the partial exclusion.
reg 1.121-3(b) states, for purposes of the partial exclusion,
Whether the requirements of this section are satisfied depends upon all the facts and circumstances. Factors that may be relevant in determining the taxpayer's primary reason for the sale or exchange include (but are not limited to) the extent to which—
(1) The sale or exchange and the circumstances giving rise to the sale or exchange are proximate in time; (is 3 years proximate or not?)
(2) The suitability of the property as the taxpayer's principal residence materially changes; (I would say yes to this)
(3) The taxpayer's financial ability to maintain the property is materially impaired; (not relevant evidently)
(4) The taxpayer uses the property as the taxpayer's residence during the period of the taxpayer's ownership of the property; (only about 5 of 8 years)
(5) The circumstances giving rise to the sale or exchange are not reasonably foreseeable when the taxpayer begins using the property as the taxpayer's principal residence; and (yes to this in my opinion)
(6) The circumstances giving rise to the sale or exchange occur during the period of the taxpayer's ownership and use of the property as the taxpayer's principal residence. (no ownership yes - use - no)
also, regardless, you'll have to recapture depreciation allowed or allowable during the rental period. this comes before the home sale exclusion.
maybe another will add a tax case or their thoughts to this.
my advice would be to sell, if possible, while you meet the two-year ownership and use test and thus avoid any IRS challenge.
