In #2, add a comma after it has begun, and a period after back. If you leave a comma after back, it is a run on sentence.

Love wandered inside, stronger than you, stronger than I. And now that it has begun, we cannot turn back. We can only turn into one.

(Not that I agree with the sentiment. You can ALWAYS stop, think, and say no.) Haven’t you heard the song Paradise in the dashboard light?

http://www.qgm.com/meatloaf/lyrics/paradise.html

Sentence 2 has structural errors:

“Love wandered inside, stronger than you, stronger than I.” is correct, but you have a period between “I” and “And.” Some editors frown on starting a sentence with the coordinating conjunction “and” because there is nothing in the sentence for it to coordinate. You can either use a comma and a lower case “a,” or rephrase to leave the “and”out altogether, starting the second sentence with “Now.” Next, I’m assuming that “ture” was a typographical error for “turn.” The section “we can only turn into one” is a clause and needs more than just a comma to separate it from the clause “we cannot turn back.” A semicolon would be good to show the strong connection between the two clauses without changing the rhythm of the sentences. A period after “back” and a capital letter on “we” would solve the mechanical problem, but would imply greater distance in the clauses than I think you intend.

Another problem for me is the content. “It has begun” is nebulous. What has begun? “It” is a pronoun with an unclear antecedent. I think you mean that the love has begun or perhaps the transformation that comes with love has begun, but you didn’t say that. I would suggest you revise to make the antecedent clear.

“rendzvous” should be rendezvous and “ture” true.