Make sure the black cumin is Nigella sativa - some things out there which are referred to as black cumin are not the real blackseed oil.

Oleander has had very good success against leukemia and I would think that continuing a good diet and lifestyle and adding oleander would be a good plan.  I would suggest two to three months of daily oleander at the normal dose amount and then backing off to a single dose every other day, given the very low Stage 0 diagnoses.

Two other items I would consider would be a good bioavailable form of curcumin (see LEF or turmeric-curcumin.com) and Jon Barron's Blood Support.  If you look at the ingredients in Blood Support:

A proprietary blend of all organic or wildcrafted
 
Red clover   
Chaparral   
Burdock root  
Poke root   
Yellow dock root  
Goldenseal root   
Oregon grape root   
Bloodroot  
Mistletoe   
Cat's claw  
Sheep sorrel   
Cayenne    
 
In a base of 45-55% pure grain alcohol

you will find some very good blood cleanses and pretty well known cancer fighters, especially among longtime herbalists.  Compare that with the cancer tonic of fifth generation master herbalist Dru Browning's and you will perhaps see why I like his product a lot:
 
http://www.tbyil.com/Brownings_Blood_Tonic.htm 

How is his throid function now?  Iodine with accompanying methylselenocysteine (the best cancer fighting form of selenium, and selenium is a must co-factor for iodine utilization) might be a good idea.

Finally, if he is not likely to do a prolonged cleanse (it actually only takes 5 days), then it would probably be a good idea to periodically do milder cleanses and take extra measures to keep the liver protected and the bile ducts open and flowing, such as:

• milk thistle
• the aforementioned curcumin and selenium
• beetroot juice
• coconut oil

I'm guessing, perhaps wrongly, that coffee enemas might not be all that welcome either?

Doing those things and continuing a healthy diet and lifestyle will likely hold him in good stead for a long, long time.

Tony