Hey there,
Does the text file follow any sort of format like json, toml, yaml, etc? Either way I can do exactly what you're looking for and do it efficiently.
I would use Go so the web ui would compile to a single binary that you could run natively on nearly any operating system. It wouldn't use many resources at all. Please feel free to look at my portfolio in my profile to see a few of the projects I've completed in the past. I'd also be glad to answer any questions you have if you message me here on freelancer.