Quote from @Kim Hopkins:
Spoke with our attorney. He confirms we can send the tenant a default letter for the subletting but that the tenant has a right to cure the default. So in theory he could get rid of all the subletting but then he'd be on the hook for all the rent.
Wait, wait, wait... You have a lease that does not allow subletting. He did anyway. He broke the lease. That contract where you allow him use of your building so long he abides by the rules is now null and void. The agreement becomes void when he no longer operates within the agreement.
I have a hard time believing you couldn't evict based on that, but I admit I'm not a commercial LL, nor in your state, but simple contract law tells me you have an out here. If the deal is that important to you, contact another lawyer for a second opinion on this. In the end, just like doctors, lawyers are just people and sometimes their judgement gets mired after seeing too many exceptions to the rule.
In addition, you COULD still try and bluff by threatening eviction papers and even providing them; It's up to your tenant to find out if you're technically (somehow) in the wrong, but it may be the push you need to get him to cooperate. Sometimes perception is more important than reality. But before you do this, sit down face to face and perhaps try and bring in a third party to increase your odds of it not turning into a shout fest. Tell him you're all about a win-win, but at a certain point he put his interests first by subletting, and now you need to put your interest first by selling.