Real Estate Excise Tax (REET) when buying out my partner

[Eva K.]

TLDR: I'm buying out my house from my ex-boyfriend in Seattle (King County), Washington and I'm struggling to find what the REET if I'm buying my ex's stake in the house. Do you pay less if its only for half the house? Is equity a consideration? I'm fairly confident from reading online we don't qualify for an exemption, but I'm trying to assess actual closing costs to trying and reduce them

All details:
Bought the house 2.5 years ago for $980K (left on mortgage $753K), we have a clause for an assumable mortgage for me to take over (I can keep same rate). We have agreed on a buyout price of $100K (initial investment) but he also wants me to pay all closing costs which was quoted $22K - That seems really high so seeing if this is accurate?

Wells Fargo initially quoted $1M value at for the house so they said $5.5K for the county tax (.05%) and $13.1K (1.28%) but a total of $18.6 in taxes but that seems really high