Re: in line fuel filter leak
If it's an inexpensive plastic filter throw it away and buy a new one. If it is a machined aluminum filter they typically have threads so you can unscrew them and take it apart for cleaning. Try tightening it.
As far as using a "sealer" what do you plan to use? Almost without exception any gasket sealer, especially those with a silicone base are not compatible with gasoline. Just read the label. Most will say 'Not for use in contact with gasoline'.
Go to any hardware store, lawnmower shop or motorcycle shop and buy a new filter. You'll want one with 1/4" O.D. Outside Diameter. While you're at it replace the fuel line too.
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