In a multi-zone mini-split setup, how do you heat heat rooms without an evaporator?
9000 btu is not two large for a bedroom, I have a 12000, and 8000 on 1 split. For 2 bedrooms, Mitsubishi makes 6000 btu so smaller units are out there for small bedrooms. 

With a mini split used for both heat and cooling I would go larger based on experience. A mini split with an inverter controlled compressor will only run as hard as is needed. If the unit is two small it will go into defrost more often and during that time the temp drops so I think a bit oversized actually helps for heating.
  I like a zone in each bedroom and depending on size 1 for the kitchen dining area and one for the family room. In my case it was cheaper for multiple compressors, allowing shorter line sets and feeders for power, so that should be investigated also. 

I think your sizing chart is off a bit, I currently have a small 3 Bd Rm house and live in climate zone 2. If I turn all the rooms on at 68f and do not run my pellet stove my units can barely keep up on a cold day low 30’s.  the house is well insulated, floors walls and ceiling. Double Pane windows and all. My systems total 48000 btu but the summer it can really freeze us out if we turn it down and that is with temps +100

Oops almost forgot how to heat without an inside unit in a room. In my bathrooms we leave the doors open, when the bathroom is in use the exhaust fan is on pulling conditioned air into the bathrooms. 
If I do not have a inside unit to a room it is usually a room that is open next to a room that is conditioned. Like kitchen/dining area where I try and have the air flow directed to the other room. In the case of not having a spare bedroom having its own inside unit we normally leave that door open and used a fan to blow air into it. Today each BdRm on my home has its own unit. I purchased compressors that were inverter controlled with the max taps I would need and added the other 2 rooms later allowing me to stagger some of the cost and not have to purchase a new compressor when I added the new zones. 
Hope this helps.