I like the recipe. But the special B (dark crystalized biscuit) malt looks just a little heavy. I would use it, only adjust it by 50%. It adds a "toffee" flavor and it is nice for complexity, but can overpower easily. It does give you a rich garnet color though.
The aromatic is a nice addition and will give you a bread-like toasty flavor. And I agree that the Munich malt is a key flavor for a Belgian abby, so you could increase that addition if needed to get to your desired OG.
Cane sugar is not appropriate in this recipe, however. It will contribute a cidery flavor and detract from the rich malt flavors. Remember, an abby ale is "liquid bread"... it's what the monks consume during the lenten fasting. It should be rich in carbs and yet warming with a higher alcohol content (7-10%ABV).
I have not used that Safele yeast strain myself. But I have used the Wyeast abby yeasts, particularly the 1762 strain which will produce a big estery note early in the beer. It mellows a little into a nice malt flavor with condition (I like to lager it for a month or 2 in a keg in the cooler).
The Wyeast 1214 Belgian yeast is also a good one as it accentuates the malt flavors a little more. But the 1762, in conjunction with the Belgian (rock) candi will produce that big "bubble gum" estery note early in the flavor.
On tap, the abby ale will pour with a thick, meringue-like head...white and fluffy, which will sustain in the glass. It is very well presented in a traditional goblet or thistle. The malt aroma is soooo inviting and the right stemware helps you appreciate it.
I like your grainbill, as it is very close to a recipe with which I've brewed many times. It has done well in competitions, so I know you'll enjoy it.
p.s.- the Mittlefruh is very much appropriate in this beer too. It is more spicy that the traditional Hallertau, but not as much as a Tettnang (which I've used too). I think Saaz could be used too, although I do indeed prefer the Mittlefruh.
Now, you've got me wanting an abby ale.