Hi Cyrix,
I doubt that you will find a web-based tool meeting your requirements. But there are a bunch of free-to-use backtesters out there. I am the maintainer of TuringTrader, an open-source backtesting engine, which can certainly do what you want to do... if you can code in C#. It comes with full documentation and lots of sample strategies:
https://www.turingtrader.org/
Cheers, Felix