What happens with the tri flow series is, they can get clogged. The way to fix that is to remove the spout by way of a 2MM screw in the back of the body. Then you can lift the spout up and clean the debris off the brightly colored flow restrictor. Then reinstall. This happens very often when homes have poor water quality. The hot and cold water is not filtered so anything could get inside there. 

Sure, many faucet manufacturers offer faucets designed for one or two holes. Most common sink configurations have either 3, 4 or 5 mounting holes on the sink top. Look under the sink to determine the number of holes in your sink because the holes may be covered by an existing faucet. Also, note that once you have purchased a faucet without a sprayer that you generally can't just add a sprayer. You need to decide before you purchase a kitchen faucet whether you want a sprayer or not.

You could, but it is absolutely not recommended. Air gaps have an health safety function and should be kept on the deck of the sink counter.

Air gaps might be a required code for dishwashers and for water softeners in many areas throughout the United States.