Yes it is OK, but why consider it? You don’t know if ESTA will be approved so reserve: London->Toronto->London and then if you need to depending on the length of your visit you may be able to get a ticket in Toronto or reserve it separately later. If the question does come up see below.
Well you know that you will be in Toronto so that ticket I’d buy. But to travel to the US just reserve a car. Reservation cancellation for a car will be much cheaper then cancelling a flight. Toronto is 8 hours drive from New York so quite a few people do it so it’s not that uncommon.
You are a Lithuanian citizen currently living in the UK. Country of citizenship being different from country of residence is OK.