It's a wonderful idea, but Support and Development mindsets are very different. You can't be good at both
I work as a developer in a medium sized company (30 devs, 10 support).
All of our internal support software is custom-made by the development team.
I have seen projects that the support staff have worked on in their own time but none that are for our company. 2 of them have Computer Science degrees, but don't have the experience to get a dev job and I think get stuck easily in support.
2 support staff have internally interviewed for a dev job and have moved up - 1 had a CS degree and was crap as a developer and has since moved on to project analysis and the other had a college HND in software and is doing well as a developer.
For me, I would say your best bet is to learn ASP.NET with MVC - this will have all of the features you'll typically need to build a great forms website. Languages needed to know or learn to be effective here are C# for backend stuff, your current database can be modelled in code (so you may not need to know SQL), HTML for frontend (would recommend using Bootstrap as your way of structuring your HTML - MVC 5 uses this and is fantastic for creating quick sites, especially those that won't be customer-facing internal sites).
There is a fantastic and free tutorial series from Pluralsight - which is an excellent resource to learn from
http://www.asp.net/mvc/pluralsightI am a server-side developer in my job mostly and I have never done any web development before, I used that tutorial series to start with and I made a dummy invoicing website for my uncle in my spare time - this gave me a lot of experience, so would definitely recommend doing side projects in your spare time.
My web site so you can laugh:
http://autoproni.co.ukAny questions just shout.