Oh dear.
I completely understand why you are in the position you are in - resolve is all well and good, but in the face of the man you love crying that he wants to be with you, it is VERY hard to see it through.
But. Unless you make a stand now, you are setting a precedent for the future that you will regret. I can promise you that. The texts you quoted up thread leave most of us in know doubt that he has shagged about - and quite possibly with more than one person. A spell in the spare room and a visit to relate is all well and good ONCE THEY HAVE BEEN KICKED OUT FOR A FEW MONTHS. That's what happens when and IF they are allowed to come home. Doing it this way means that you are skipping/leaving out the crucial lesson in all of this, which is that cheating has consequences.
The message he is getting is that a bit of crying, laundry,breakfast in bed and a couple of weeks in the spare room is his punishment but that broadly, he is forgiven.
I am so sorry if this sounds harsh but I realise you must be exhausted, drained, confused and tearful and frankly the last thing you want is to break up your marital home just before Christmas. But you are not - he has already done that. It might not be forever - in which case throwing him out is more important than ever.
Equally, it might be forever. So you should know one more thing.
You said up thread that he is 'the father of your children and you will always love him'.
He will always be the father of your children but you will not necessarly always love him. I bet if you polled MNers who felt this about their spouses you would be AMAZED by the number of people who fell out of love with their partners far more quickly than they ever imagined they would.
I really hope this isn't too brutal - you sound lovely and deserve happiness.