1. 雨で服がぬれた。
The/my clothes/clothe got wet under/in the rain. Correct.

2. 床がぬれています。気をつけてください。　
The floor is well, so please be careful. Typo! well >> wet

3. 君の涙でボクの胸がぬれた。
Literally, "My chest got wet with your tears."

4. マリアと２年前に別れた。
I parted with Maria 2 years ago. Correct.

5. マサさんと別れたくない！愛してるから。
I don't want to separate with Masa because I love him. Correct.

Thanks masaegu san. Do you think is possible to say:

1. (僕の)服が雨でがぬれた。

4. ２年前にマリアと別れた。

By the way, somehow I feel that I can also translate "雨で服がぬれた" to "The clothes got wet because of the rain". And also this sentence "君の涙でボクの胸がぬれた". Do you think I can translate it to "My chest got wet because of your tears.

The reason why I think that it can be done is because I remember that "で" can be refers as "Because". Not sure if I am right though.

#4 is correct.

#1 is incorrect. One cannot say でが in any situation. Need to drop the second が.

Yes, you are right about the で.

Thanks for the help, masaegu san. :)

There is one more question that I almost forget to ask, and that is regarding "ぬらします".

I was wondering what is the difference between "ぬらします" and "ぬれます"? And also if I can say "床がぬらしています。気をつけてください" instead of "床がぬれています。気をつけてください"?

The difference is the transitive vs. intransitive once again.

ぬらします = transitive. You wet something.

ぬれます = intransitive. Something gets wet.

You cannot say 床がぬらしています. That makes little to no sense because it's saying "The floor is wetting (another thing)."

はい、分かりました。本当にどうもありがとうございま した、masaegu さん。:)