$3,000,000. - 1,230,000. = 1,770,000. + depreciation = gain.
$3,000,000. - 1,835,000. = 1,165,000. maximum deferral.
Presuming the 1,835,000. is as you represent (I'm not doubting) is a qualified exchange.
You are representing that this $907,000. is a lease.
I would question if it was actually a sale?
Analysis of the transaction would also require a review & probably an appraisal to determine your allocation of the $3,000,000. purchase price, the terms of the proposed "lease", etc.
I believe that as you suspect, your new investment for purposes of the 1031 may be $928,000. as this is all part of one transaction, and the "boot" comes off the top in terms of what is taxable.
Way too many variables here. If I were you I would get a written representation of the tax treatment from a tax attorney (CPAs can't give these type of written assurances);
Too much money at stake here, not to be certain up front. Both the CPA & attorney should bless this & the Attorney should commit to it in writing, which is routine for a tax attorney.