Probably late to be chiming in, but, what you have essentially done is taken the leg work out of searching for flights on meta scraper sites like Kayak, Google, etc. Even though those sites allow you to setup alerts and monitor prices, it can be overwhelming if you are not willing to put in the time.
When I saw you were doing this manually I was not totally surprised because you are not a programmer but you are a problem solver providing a service.
What you have done to this point is proven there is a market for your services, and with that proof now in place, if you had a long-term business plan and growth strategy you could turn this into a much larger operation.
How? The first step would be to automate the searching, but that's obvious. The not so obvious is to undercut the services you rely on to get your information and go directly to the sources, and capture some of the booking fee market that your competitors receive when someone books a flight through their service.
Google, Priceline, Kayak, etc all monetize from the booking. Your model of monetizing from searches is a different approach, and might work in the early days for awhile, but for long-term sustainability you need to find a way to create an algorithm that replicates your searching, apply some human filtering as needed, and then work the backend by going after the booking business.
At first you could monetize both phases until the bookings makes you enough revenue you can justify making the service free for most and then subscribers could pay for more of a virtual travel agent type service where you have a department that handles calls/emails/contact and filters results.
At some point you can expand this to include hotels, cars, cruises and every form of travel by going straight to the source and working out a fee for booking, and maybe even some agreements for yourself to offer some limited exclusives.
Today, you are a glorified travel agent for thousands of people. Tomorrow, you could be the next Kayak or Google Flights and making millions in your sleep.
Keep up the good work!