WA commerical landlord tenant act, tenant's responsibility for early termination of lease

The WA landlord tenant act only applies to residential property. You need to look at the lease to see if there is any language regarding default by tenant. Landlord does have a duty to mitigate his damages in the event of tenant breach, but you would have the burden of showing that the rent amount was so commercially unreasonable as to be a de facto refusal by the landlord to mitigate. Bottom line: you don't have much recourse to the landlord's actions at this point, absent some provision in the lease. You may want to look at the lease and see if you have the right to assign the lease or sublet. If so, it may be an option for you to find the next tenant and assign (preferably) or sublet (you still are responsible for lease payments)

You might have a defense if the landlord is seeking a rent that is far above the market. For instance, if the market dictates that the landlord could get $10,000 per month, but the landlord is asking $20,000 per month, the landlord is not being reasonable. You could argue that the landlord has failed to mitigate damages. If succesful, the landlord would not be entitled to damages against you.

You should review your assignment/sublease provision in your lease and attempt to find a tenant to step into your shoes.