My wife is asking me to leave the house for a period, no more than a month, but I am afraid she will sue me for abandonment trying to obtain full custody of our one and a half year old son.

First, she can't sue for abandonment under these circumstances. She might be able to file for divorce and use your leaving as grounds.

So if you want to protect yourself, ask her to provide you with a letter requesting a trial separation. In any case you make sure that you continue to see your child and provide support.

If this is a trial separation, it might not be a bad idea to ask to have a child support order put in place, and a custody agreement. Child support payments paid through the state are much easier to prove in court than a "he said she said" situation if you simply buy items for your child. I wish you luck.