Faule Ilse double Seelenbalsam and Brandstifter will set enemies quick on fire and heal you in the same time but its CQC and not for medium to long range, so thats why its only in the front and not on the sides.

Brand-Bombarde III do alot of damage to fleets of ships and can destroy them pretty fast when they are close together

Landwurm-Luftverpester, Kupfer-Befestigungsstation and Teufelsgebräu boost ALL secondary effects on the FB3 because they count as all 3, so Shock, Burn and Explosive weapons.
Statische Aufladung boost works perfect on this dual Shock and Burn build
Stopfstation für Munition and Bombardenwerkstatt I are a no brainer for this bombard build.

Playstyle Tip:
Dont stay still with this build and try to keep circling the enemies, staying still can sometimes work if the enemy is focused on someone else but most of the time keep moving.