Hi again! Hope you are feeling okay today.
Previously, you mentioned you have suffered with depression but are done with that now. I am making a guess, but was part of it due to a difficult childhood? You have a critical inner voice by the sound of it and, although you say you are not depressed, the voice could be a remnant of what caused depression previously. Possibly, looking at the reasons behind your critical inner voice might help in the long run as I don't feel, from what you have said, that you should feel guilty about wanting time to yourself or looking forward to it.
Rather than lowering standards think of it as prioritising. Does the kitchen need to be really clean or would you be better off doing something you enjoy? Is a cleaner a possibility? Between work and a child you need fun, when possible, instead of spending your precious spare time cleaning. I also recommend a massive clear out, regardless. You do feel more organised and lighter after it. It is much easier to keep the place clean afterwards.
If you still think there is an issue go to the GP and have them run a few tests- you may be anaemic/ lacking Vitamin D which could be making you feel worse.
Additionally, don't underestimate lack of sleep and what it does to your mind. Do you have family or friends there who you could leave your child with while you had a weekend of relaxing with your husband? If not I suggest you speak to your husband and explain how tired you are and that you would like a spa break (or something) and are booking one for yourself. I am sure he will understand and will be able to look after his own child without you for a night or two.
I also recommend starting a thread in Parenting as I am sure you will find a hoard of honest parents who also prefer spending some time alone to playing kids' games. You are not alone in feeling like this. There are plenty of mum blogs detailing feeling like this.
My final point would be based on the fact that you say you enjoy sorting other people's problems so flip this around: if a close friend came to you and said everything you have said here, what would your advice be for them?