@MasterOfTheWind

I think what you are trying to do is very complicated and you have to have quite some knowledge to get this working.
So many people can't help you with that.

Have you looked into an easier solution ?
You can use the "CVBS/Composite Video" output of the Raspberry pi if your TV supports it.
The the quality of the CVBS/Composite video signal is quite acceptable on an old TV.

If your TV is LCD, old LCD, then you need to use the best inputs the LCD has. Since it does not have HDMI, then what is the next best input ? VGA ? Component ? Scart will not look very good on a LCD, old or new, since the TV will likely be handling the scaling.

I wouldn't go for the rgbpi, the website isn't secure, they do not have any prices online - instead you have to send them your personal details just to get a price, and even then there is nothing stopping them from pricing you by region, not by the product itself - everyone gets a different price based on where they live. And, looking at many forums (I have researched this due to wanting a SCART output) they have many bugs in their software they link to.

I would get a PiScart, if it's scart you want. Or, get a HAT with VGA - if your TV has VGA.

Yes @shazza6887, this is the way, but you do not need to use VGA to Rsinc adapter, you can use a vga 2 rgb cable (like this https://www.amazon.com/VGA-RGB-Cable-Male-1-8m/dp/B0096TTOHG) or and VGA to Scart (in this web explain how to make the cable http://www.idiots.org.uk/vga_rgb_scart/)
And force the pi to output at 15khz (https://github.com/raspberrypi/firmware/issues/637 this way have some problems only if you want to use multiple resolutions).