Good news about the job! Even if it isn't the perfect fit, it will give you breathing space to find something that you are happier with, without the stress of being out of work!
Well done on realising how you must have come across to your OH yesterday. I recognise the problem, but the other way around, I am the one holding back my OH and feeling guilty about it. At least you have recognised it now.
I guess it will be difficult for a while as you get more energy and want to be exercising more, It must be difficult for your OH not to resent the changes. I know that someone telling me to lose weight, exercise and "get moving" tended/tends to have the opposite effect! It is going to take some adjustment for both of you as you are going through these changes.