Good evening, Winking Weasel
You have chosen an odd goal as a character. Most people would consider becoming a weaseller less than a side quest. Getting the achievement shows an appreciation for the little fellows, or that you enjoy the ridiculousness of it. However in actions, echoes or words it is only a small goal, technically achievable within a day for late game players.
Others strive for Paramount Presence, Poet-Laurate, Couriers Footprint, Hesperidean Cider, a Heptagoat, the Seven-Fold Knock, the content boundery of their Ambition, exploring every location, getting every companion, etc, etc. There are many goals you can set for yourself. There is no reason to venture North if you don’t want to, and enough to do if you change your current mindset a bit.
If you want to stay in character you can still set your goal to an insanely high number of weasels. The arbitrary 400 that Failbetter Games gave us doesn’t have to be your limit. Getting thousands, or tens of thousands or even more of a certain item isn’t unusual within this community. (On the forums you may notice a lot of goals of players involving getting high numbers of sevens, like 77.777) You can do the same for Araby fighting weasels.
You already have a salt-weasel, but do you own a celebrated weasel? If not, stick around at least till next Hallowmas.
The main use of weasels (if you don’t intent on feeding them to tigers or carnivorous plants) is giving them a happy home with an urchin, so another goal could be maxing out your Renown: Urchins. If you choose to do so, then you may pick up What Might Be a Thunderbolt on the way, which also is an interesting quest.
Hope this helps!