If you want an authentic tasting Northern German altbier, I'd suggest changing up the recipe in several ways.
First, I'd use noble hops for bittering. Since altbier is a very clean beer with a good amount of bittering, I think cascade would be discernible and out of place. You want a firm hop bitterness, but restrained hopping, if that makes sense. I wouldn't use late hops at all, but the saaz may leave a spicy flavor that is weird in an altbier. I'd use a neutral hop for bittering, like Magnum, or a noble hop variety like tettnanger and that's it.
It should also have some bready or biscuity notes, and not just caramel sweetness. It should also be fairly dark colored.
I wouldn't use US two-row or crystal malt in an altbier. I would use Munich malt and pilsner malt, some carafa special (for color), and a tiny bit of caraMunich for the crystal notes. I've seen victory in altbiers, but never used it myself, and I've liked it.
As far as fermentation, it really has to be kept cool-ish. I've used Wyeast 1007 with great results. I used it at 60-62 degrees, and loved it. If you went any higher than about 65, it might get excessively fruity. That strain seems to take forever to clear if you're not filtering (I don't) so you may want to go with a more flocculant strain. I'm not sure of the one from White Labs, but that may be a good choice.
To control fermentation temperatures, you could try sticking your fermenter in a cooler with an ice and water bath. That's why I do, since I don't have a spare bathtub. I even made a foam lid out of foam insulation, which is probably overkill but I only change out the frozen water bottles about once a day.
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