@gtbrien,
gtbrien wrote:"Praise to our gracious and merciful God, our strength."
"Laudamus ad Dei comis et miserecordis, fortibus nostris."
Let's start with "Praise". You have translated it with the Latin for "We
praise". If that was your intention, good. Other ways include
Laus -- The noun "Praise"
Laudate -- "Praise" as an imperative
Laudemus -- "Let us praise"
If you want to use the noun
Laus, then the form of
Deus to use is
Deo
(without the preposition).
If you want to use one of the verb forms, then use
Deum as it will be the
direct object.
As for "gracious and merciful", I would follow the example of the Latin
Vulgate bible and use the adjective
clemens for "gracious". So:
<noun>
Deo clementi et misericordi
<verb>
Deum clementem et misericordem
I would use
fortitudo for "strength". It should agree in case with
Deo
or
Deum. So:
Deo . . . fortitudini nostro
or
Deum . . . fortitudinem nostrum