If the felt is thin with not enough meat to pounce a little I would try a 3M white non abrasive pad. I use them to 'polish' the felt. It gets the felt fibres aligned with the nap without removing any fibres.
I picked mine up on Amazon. The 3M ones are pricey but Mercer makes some that look the same and are cheaper.
Short of not having been sanded by large grit paper or brushed with a wire brush, it looks like it's unfelting. It could be caused by a poor felting process & some cheaper felts can start to fall apart if they are 'over' manipulated or repeatedly creased. If it is bad felting then there isn't a great deal to be done. Careful sanding may render the surface a little smoother (if there is sufficient thickness of felt) or spraying with a fine mist of alcohol & flaming it but if the fibres are disconnecting, you can't force them back in, even by hitting them with a hammer.
On the lower cost Stetsons they have been known to use..."Genuine Leather" in their sweats which is a euphemism for reconstituted leather made from the residue left over from the tanning process. It is terrible stuff.
It is not that hard. There are a number of Etsy sellers....FineVintageFedoras sell them and you can buy them cut and sewn to your size. Once you receive it I can walk you through it. If the hat fits you then remove the sweat, separate it at the join and measure it's length. That way you can order an accurate replacement.
Great hat! Definitely 1940s or ‘50s but others here might know more.
