Every person who signs the lease is responsible for the entire rent unless the lease limits the liability of one party. As I recall, the one time I encountered a tenant who got rent paid directly by the government, the landlord had to sign a gov't lease that supplemented the regular lease and limited the government's liability to the authorized monthly rent subsidy. If you had roommates, you need to drag them into the suit and cross-claim against them for the rent.
Did L send you a statement of deductions from the security deposit within the time limit established by state law? State law may require him to refund double your deposit if he didn't. This would nicely cancel out the alleged rent shortfall.
Go to your social services person and get copies of all payments they sent L, & copies of what you paid L. Get back to us with more facts (like your state) and more specific questions.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.
