Does the "e" of "ea" palatalize the consonant that precedes? For exemple in "breaca" or "bearead"... I heard these words pronounced with broad b/r consonants.
And, in general, is there some cases when consonants near to "e" or "i" remain broad?

(p.s. sorry for my english, if there are some french speakers it'll be easier for me to communicate; otherwise I understand quite well)

Yes. But an "r" at the beginning of a word is always pronounced broad, at least in the dialect I'm studying.

there is not only the "r" pronounced broad (and not only at the beginning), but also "b" and some other consonants I heard. (I mean, in general, the cases when "e" in "ea" is not fada)

And I'm not sure if "ea", when not preceded by any consonant, is pronounced "a" or "ya".
like in "an ea", ("ní hea")
in my native language there is a separate sounds ya, yu, etc., broad and slender variants of vowels, not of consonants, that is why I'm a little confused...

By the way, Celtoid, which is the dialect you're studying?

I'd say it'd be pronounced "a" (as in "bat"). I'm studying the dialect spoken in Cois Fharraige, Co. Galway, from "Learning Irish" by Mícheál Ó Siadhail. Céard futsa?