I have set up an entire educational website containing dozens of HTML5 apps created with Fusion 2.5 and I can confirm that this is a very very solid product with tons of support. It is by far the best product out there for creating online apps in HTML5. I have many apps that are multi platform in HTML (PC, Mac, iPad and Android tablets) and they work perfectly across every version of Chrome, Edge, Safari and FIrefox.
I would not have any worries about investing money into purchasing Fusion and the HTML5 exporter. It's more than worth the money!
One thing that never worked ( for me ) on the Html5 exporter was the compatibility with mp4 videos. Does someone know a proper solution without linking the video to an existing server to make it work?