Voluntary disclosure is a good thing, so you have that.
I'm a little bit confused about a 2 to 3 week EA and a voluntary confession with 3 d days? I'm also dubious about there being no sex when there were multiple lunch and dinner dates with some physical contact. It's possible there was nothing physically sexual, but unlikely if there was opportunity. These are things to think about.
One thing that's pretty consistent is that cheaters lie. It comes with the territory. You can't conduct any kind of an affair without deception, obfuscation, or lies. Its very rare for a wayward spouse to tell the whole truth, the whole story, right off the bat. The fact that he voluntarily confessed is a good thing and might put him in that rare category, but I wouldn't just assume that.
As far as "severity" goes, it can be argued some affairs are worse than others, and if what you're hearing is accurate this affair would register fairly low on the severity scale, but... no matter what happened there was a betrayal. I've seen it said that no matter the type of affair it was, it's always severe to the person experiencing the fallout.
Some people feel that exchanging kisses can be worse than just straight up sex. For instance, a spouse using prostitutes might not be as severe to someone as there being actual romance involved. Hand holding, kisses, and exchanging "I love yous" without sex could be perceived as "worse" than visiting prostitutes. It depends on the person. I personally think EAs can be just as bad a full on physical affairs.
The struggle to send a NC message is a red flag. Worrying about hurting AP's feelings while you, his wife, are bleeding out from the wound of betrayal is a red flag. That should happen ASAP. What's more important? Saving your marriage or protecting AP's feelings? A truly remorseful WS is willing to do anything it takes to save the marriage. No contact is the very first, most basic step in that process. Your feelings should trump all others in this situation.
It's not about getting through the first few weeks. More like the first few months. Betrayal trauma is real trauma. The general rule for recovery is 2 to 5 years, and that's when everything is going as well as possible. My d day was well over a year ago and I'm just now starting to get my feet back under me. I don't think you're even going to begin to start healing until that no contact message is sent and all ties are cut with her. If they're still in contact the affair is still ongoing.
What you need to know is that none of this is your fault. No matter what was happening in your marriage there's never a justification for an affair. You said that the marriage was going well before so I'm assuming he's not pinning any of this on you, but if he is, it's just a load of crap. No marriage is ever fixed or made better by bringing a third party into it.