How can I combine lightbulbs of different types and specifications to accurately simulate medium-intensity daylight in a domestic setting?
I have basic knowledge of what we did in a industrial plant to combat SAD so this answer covers what I learned when we changed the lighting to reduce the affects of SAD at our facility. 

In our office areas we used 50% 6500k lighting and 50% 4500k lamps were matched with each ballast or 2 lamps at 6500k on 1 side and 2 at 4500k. Matching lamp type extends the life of the pair of lamps and reduced ballast problems.

In walkways we used 6500k lighting 100%  

The reason for the difference was when walking the 6500k was closer to true daylight and the affect was similar to exercising out side even though just walking. 
The reason for 50/50 split was that 6500k was hard on our eyes when reading so reducing the level and mixing with 4500 ended up being the best over all. 

We also had clean room areas that they wanted to get similar results however 6500k has two much blue light and was a problem for photo lithography (the process of making different layers on wafers). Some rooms only have yellow light no blue at all. The 6000k light was the max we could use without affecting the processes and still get some advantage from the light. 

The last thing we did was offer some very concentrated UV lights in the bathroom lounges. Designed for short exposure on the neck and shoulders. 

The results after several years was an increase in productivity and a reduction in accidents and sick time taken. I was a manager and I saw all the reports I think it was 19% improvement with no other changes attributed except lighting. 

We did not work with 2500k-4000k at the plant but occupational Health and Safety recommended that in our homes we use 3500k lamps in areas like bed rooms because the bright white / blue lights affect our Circadian Rhythms and low levels of yellow / orange lights are more natural and if dimmed tell the body it’s time for sleep, where 6500k says its day time get to work. 

We were told that the blue / white lights on the back of the neck , shoulders and head was the most effective location for intense light therapy. 
This site is in Corvallis Oregon and at one time the site had ~10k personal working on the site. Prior to the rollout of 6500k, 5000k, 5500k &amp; 6000k lighting levels were also tested in different areas of the plant. 

I think your plan to have the light to the rear as you mentioned is a good plan from what I had learned, I don’t know if the 3500k is really needed I remember that low levels did not affect the body in a negative way where sleeping was concerned but 6500k may prevent a person from sleeping up to an hour after exposure depending on the intensity. 

I would get some additional references material on SAD as there is a ton of info on the web today. The lighting work I am describing was done 25years ago and they still use the same color frequency except in areas close to photo they went to all 4500k as geometry of the components got smaller the light had a larger affect. 
Hope this helps.

I just remembered, we had to remove the plastic bezels in the lamps and installed reflective grids , the plastic was absorbing the blue light and we had to have some kind of covers so the reflective metal grids increased the light as measured at desk top level. I do not remember how many foot candles / lumens the target was.