Unless I really had to look at this in a particular way, I'd start with simple frame analyse and move on from there. These types of things are only as complicated as you want to make them.

Use your numbers to plot a bending moment and deflection diagram and you should start to see what is transferring load and to where. Once you can see how the structure is reacting (and then plot the reaction vectors at the connection points due to the deflection of the the horizontal member), it should become a simpler to see what you are trying to calculate.

The confusing part comes (probably) from the numerous quadratic equations you could jump through to try and predict all possible outcomes for this given scenario, so look at it's simplest form and go from there.

If you have the forces (moments and shear) at C & D already, You just need to apply them. Equal and opposite, remember?

You have fixed bases and what looks like pinned joints? If so, simple pinned joints cannot transfer moment, only shear; so work from that.

This is a rambling reply but it's been a long few months, so, sorry.