What you are feeling is entirely natural, precious. When you left stbxh your emotions were on full power high octane adrenaline and during the past few weeks you've had incredible highs and lows but your eyes were set firmly on a target - namely, your application to the Court and the date of the Hearing.
You then experienced a moment of exhilaration, a vindication of your actions, followed by sublime relief, as if a weight had been lifted from your shoulders, but now you're back to the daily grind and having to play a waiting game until divorce and finances are finalised.
However triumphant you felt at being able to move back into the marital home, it may now seem as if you haven't 'moved on' and, of course, the very bricks of your house together with the contents are continual reminders of the history of your relationship with stbxh.
If there are items that have memories attached that are not needed, either junk them or store them away somewhere they can't be seen. Re-arrange furniture, maybe even move rooms around - swap the bedroom you shared with stbxh with one of the dcs and buy new bedlinen.
No matter how low the outside temperature may be at the moment, pick a dry day and open every window and door - let some fresh air in to clear away any residue of stbxh that may be lingering. Clean the windows, wash curtains and any fabric items that may imprinted with unwelcome scents.
Consider painting the hallway a different colour so that you have an impression of walking into your new home everytime you enter the house - because no matter how much you revisit or are reminded of the past, you now have the opportunity to make the house you live in yours.
Of course you're exeriencing feelings of 'is that it' and you're going to have days when you feel low. You mentioned that you'd thought about leaving stbxh a couple of years ago and whenever, or however, you left your marriage, you'd be experiencing the same feelings of an anti-climax.
Adjusting to life as a single parent after divorce/separation can be a slow process and, no matter how amicable the event was, it can be accompanied by feelings of sadness, anger, grief, despair, and hopelessness, among others.
Gradually, the dark clouds do lift and please be assured that the sun will shine for you again once you have recovered from the shock and trauma of the recent past, and have rediscovered yourself. In the meantime, watch as many comedies as you can because laughter is the best tonic for low spirits.
You mentioned that the possibiility of moving to a smaller house after divorce - start looking online and in local papers/estate agents' windows to see what's available with a view to working out the type of house that you would like to live in.
Picture your dream house and imagine how you'll decorate it, furnish it, and how you'll feel living there. ' See' the future 'you' want for yourself and dc - and make it happen.