De profundis clamavi ad te Domine = Out of the depths, I have cried to you, O Lord.

and,

De profundis clamere ad te domine = Out of the depths, I cry to you, O Lord.

while,

"De profundis clamo ad te domine" = boo-boo ?

No. Your second sentence is ungrammatical.

1. "De profundis clamo ad te domine" = 'I cry out to you from the depths O Lord.'

2. "De profundis clamavi ad te domine" = 'I have cried out to you from the depths O Lord.'

3. The infinitve of clamo is clamare. You could ad another verb into the mix for something like: "De profundis volo clamare ad te domine." = 'I want to call out to you from the depths O Lord.'

Ceci n'est pas un seing.