Hello, forthe best. I lurked on your other threads and didn't post, but just wanted to join in now with encouragement.
You said "He still wants us to get back together and has basically said he will change etc." That is: he will change. He has not changed yet. By contrast, he doesn't sound as thought he even understands what it would mean to change. What is he looking forward to? What is he planning? Has he any hopes? You describe nothing , beyond "getting back together with you", and that is not a long-term plan; it is not a detailed plan about how to behave.
It has only been two weeks. With no job yet (I would imagine, given the GP appointments), the time no seems longer to him, and he has nothing to do but think about how slowly the time is passing.
Keep asking yourself: if you "take him back", what then? You won't have any leverage over him. Your DDs will be brought back under the strain and shadow of living with someone who is not all there, who mopes around and has no plans. Even if he is not smoking at the moment, he still has little to offer because he has given up all his interests.
You are tired, but that is a reaction to ages of strain - your body can finally relax and catch up. The irritability is also a reaction to the long period of strain, but also the conflicting pressures now of living your life according to your own timescale (going to work, living with the DDS, etc.) and being made incredibly aware of your OH's empty, stretched-out timescale (where nothing happens, and the future is an eternity unless you "take him back" - and his horizon ends there).
Please don't be surprised and discouraged by how you feel at this stage. Your life has changed, and, yes, you will need to start living differently, and there is a risk that you will miss opportunities. But you need to recover before you start trying to choose between new opportunities!
As for the "safety net": you were his safety net, and if you take him back, you blow it for both of you. And for your DDs.