I bought this guy as a 4ft bare root whip back in late Feb. I stuck in a wine barrel for a while and it wasn't doing well. I then planted it in the ground against a north facing fence. You can see there has been minimal growth. What would be best for this tree.

Air layer off the top in early summer and put that somewhere sunny. Although, VdB is a smaller tree and will take longer to grow above the fence so maybe that is not a good spot for it after all and it should move.

Why not just move it? Why air layer? Is there a chance of losing it?

Water more frequent,if you can,that will get it grow faster in your dry climate.
Of course if moved in full sun and watered,more often,that will make it grow.

Don't move it. Water more & give it some shade.  Weekly weak dose of fertilizer would help.

I think what Herman mention in post 4 is sound advice.
Water and sun once it starts then give some fert but never when surrounding fig soil is dry or you simply burn the roots.

There are many factors which determine how quickly a tree will grow.  If any one of them is limited, the growth of the tree is slowed.  Resolving one limiting factor doesn't necessarily produce more rapid growth if there are others.  Also, an excess of one factor doesn't alleviate the a deficiency in another factor.  So if the problem is not enough sunlight, more fertilizer will not over come this problem (and may cause other problems) if the soil already provides sufficient nutrients.

It looks like your PH is growing well.  So we can examine some of the similarities and differences to the two trees to try to find the reason for the disparity in growth.

Similarities:

• In the same yard, so pretty similar soil conditions
• Same care taker, so pretty similar care (i.e. feeding, watering, etc.)

Differences/Possible Problems:

• Growth Habits of the Varieties: VdeB is considered by most to be a slow growing tree.
• Access to Light/Heat:  This can have an impact on growth
• Disease: Check for FMV and RKN
• Timing: Was the PH and VdeB put into the ground at the same time? or was the VdeB put into the barrel when PH went into the ground then moved later?
  
• Other problems which may not be immediately evident

Given the time it has been in it's current place, it should not be too difficult to dig it up to move it.  Whether or not you choose to move it, inspect the roots for RKN galls.  Also, understand, if  you do move the tree, cutting the roots again will temporarily set your tree back again.  So do not expect it to catch up to the PH so quickly. 

~james