The Airstream weight is empty except for propane gas. The meaningful weight would be loaded for camping, as you might load it. The 23FB has most of the storage forward, so is likely to increase tongue weight significantly.
Not sure if you are matching this to a tow vehicle or perhaps picking a weight distribution hitch, but the only way to be sure is to weigh the tongue when loaded for your needs. There is a simple technique using a bathroom scale.
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