(1) An attorney will have to take a look at your lease. Commercial leases can be incredibly complex. You're lease may have completely expired. Then again, certain provisions in your lease may still be enforceable. For instance, there may be something in your lease that grants the landlord a right to change the locks upon non-payment. I have seen leases that became month-to-month, BUT where certain provisions of the original lease were still in effect.
(2) Your position is not overly strong. You may have some damages, but you will have to give careful consideration to whether or not it will actually be economically worthwhile to initiate litigation. No attorney that I know would take your case on a contingency fee (hoping for a % of the damages recovered). That is too speculative. Instead, you would have to retain someone and pay hourly. Given that you are in chapter 7 and you are behind on your commercial property rent, any attorney who takes this will want a healthy retainer up front for fees plus money for costs. Just throwing number out there-- someone might take this for $2,500 retainer plus $1,000 for initial costs (filing, service, etc).
If you filed bankruptcy tell your bankruptcy attorney what your landlord has done. It may be a violation of the automatic stay which your landlord may have to pay sanctions. Best to ask your bankruptcy attorney.
It sounds very likely that the landlord may have violated the automatic stay that you benefit from while your bankruptcy case is open. The bankruptcy court can sanction the landlord and issue an injunction to control the landlord's future conduct. You should contact a bankruptcy attorney immediately to discuss this.
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