Hello!
As Raspberry Pi expert and HTML/CSS/Js developer I confirm that I will do this task in 6 days for the mentioned budget. Some days ago I worked on a similar project for my local customer. I know a lot of web interfaces looks and approaches for different routers. So I could easy perform your task.
You will have all the code, sources, files, etc.
Feel free to ask the questions. Let's discuss and start the project.
Regards,
Vitaliy