Went through something like this a year ago...Please go through your lease agreement word by word on the part that talks about breaking lease for you and the owner. Did you sign any part that allowed the owner to cancel lease at any time if they were selling the home?
If not, typically, the lease is a contract and the owner will have to keep his end of the lease. If the owner puts it on the market, he will have to negotiate with buyers and disclose that there is an existing lease. Most buyers won't mind a current tenant if you pay on time but some will pass.
If he's pulling you hard to move out, I would negotiate with him a "price" that it would cost for you to break your contract and move out within 30 days. Perhaps a months rent and full security deposit back may be fair. You live for free for a month and find another place to rent. It's a great time to sell now so I'm sure the seller has incentives to take any deal you offer
Best of luck! ps I'm no realtor or lawyer