I'm sorry to hear about your wife's depression and the effect it is having on you and your marriage. I also suffer from depression and have been married to my husband for almost 33 years.
It is so good of you to be concerned enough to write a post on this site. You will get a lot of encouragement here. Your wife would also benefit from this site! But maybe she is not ready for that yet. I would advise you to not consider bailing out. I know it must be difficult the way things are going right now; you probably feel like you have to walk on eggshells and don't know what to expect from one moment to the next. But keep in mind that your wife is finally going for counseling and has more appointments in September. Give all of that a chance to work. If she is not on medication, maybe she needs to be.
As far as what you are doing, it sounds like you are doing all of the right things. My husband has never dealt with my depression well; in fact, he is notorious for doing all of the wrong things. These are things he has done over the years: gets angry at me for being depressed, picks a fight with me while I'm depressed, turns a cold shoulder on me (especially in bed), gets depressed himself, or just sits back in silence for days waiting for me to get over being depressed by myself. All of these are the wrong things to do. I am surprised that your wife wants to sleep on the couch. Have you asked her why she feels the need to do this? When I am depressed, I need my husband's arms around me; especially at night. Otherwise, I cannot sleep. That's where his cold shoulder really wreaks havoc on my already depressed condition. I would encourage you to encourage her to discuss this with her doctor. This is not the time for the two of you to be apart at night. I hope she can explain to you why she feels the need to do this; and especially hope she discusses this with her doctor. Could she be going through some kind of post partum depression? I know your son is three, but maybe this has been brewing for awhile?
Trying to be upbeat and not take her moods personally are the right things to do. In fact, it sounds like you are doing all of the right things right now. But please, don't think about bailing out. Think about the consequences of this; for your son, your wife, and for you.
I hope you continue with this site as it will help you tremendously. There is so much support here.
Diagnosed with: seizure disorder in 1962; seizure-free since 1969, anorexia from 1968-1969; IBS-D in 1996, Mild depression, anxiety, & OCD in 2000, (probably had since childhood); PMDD in 2001, Dysfunctional tear syndrome in 2009; Meds: Phenobarbitol, Paxil, Allegra; Supplements: Citrucel tablets; many vitamins, minerals & herbs - too many to list here