How would I dramatically improve on the damage? Try to get the weapon to +10? I don't know if it can scale higher than that.
Can I buff the weapon further with faith spells? Maybe I should I invest in faith. My damage right now is kinda not that great.
Yes, one way is to get the the weapon to +10.
Since you are using the bloodfang, it scales well with Dex (c). And moderately with strength (d). So put points into these.
The spell Bloodflame Blade, works very well with that weapon. It Drops by a Teardrop Scarab in the marshes northwest to Rose Church, in the southwest area of the lake.
The Bloodhound's Fang also has a very good Ashes of War, that deals 2 attacks and has a generous invulnerability window.
That weapon also has a great scaling with jump attacks. So you an run at an enemy and do a jump with strong attack will deal a lot of damage. The Claw Talisman ads 15% to jump attack damage (7.5% in pvp). It's in Stormveil Castle.
The Raptor's Black Feather also boost jum attacks by 10%. But it's further in the game, in the Sage Cave.
It can also be buffed with greases.
The heavy attack can deal a lot of poise damage. A lot of enemies will go into stagger with a couple of strong charged attacks. But it's slow to use.
Using it single hand, also increases damage. But then you cant use spells or shields.
Also, very important. A heavy weapon like that, uses a lot of stamina. So consider using the Green Turtle Talisman. This boosts stamina regen and it's extremely useful in combat. It is in the Summonwater Village.