RD4 - Kenwood / Pure DAB adapter

[Harrythephot]

My 2016 Tepee has the basic RD4 unit with the RCA jacks in the glove compartment and no usb or bluetooth.

Rather than fight with configuring an aftermarket head unit, I've ordered the Kenwood version of the Pure Highway 600 (KTC500 DAB) to add DAB and Bluetooth hands free to the car.

I can link it to the RD4 using FM or the RCA jacks, but I have a few questions;

1. Is there an easy way to add a stereo socket to the RD4 unit, in addition to, or replacing the RCA sockets?

2. Best place to take switched power from, for an additional 12v USB socket?

3. Does the 70cm long fibreglass roof aerial support DAB, so I could split the signal rather than use the Kenwood windscreen aerial?

4. If not, how straightforward is it to get to the roof aerial fitting and replace it?

Sorry for so many questions and thanks in advance.

[Brixmis7]

This may be of help... https://www.youtube.com/watch?v=1kTnwHXlVYE

[Harrythephot]

This may be of help... https://www.youtube.com/watch?v=1kTnwHXlVYE

Thanks for the reply. 
Unfortunately the Pure videos and most of the others, only cover the generalities of fitting the DAB unit into "A" car.

Because the RD4 unit is tied into the vehicles computer, along with much of the wiring, it makes what used to be very simple things a lot trickier.
That said, I've found this;

https://www.ebay.co.uk/itm/363125040849?ul_noapp=true

Which I hope will let me replace the RCA adapter at the multi connector and fit a female mini jack in the glove compartment with

https://www.ebay.co.uk/itm/3-5mm-Jack-St...4513843119

And add a fused power supply with

https://www.ebay.co.uk/itm/Car-12V-24-Ci...4321368505

If I can find a switched power supply that isn't going to upset the computer.

For now I will use the supplied windscreen aerial for DAB, but slow time, plan to utilize the cars external aerial.

If I can get it sorted, I will post the details here, so it's around for anyone else who is in the same situation.