King David's accomplishments:
anointed king over the house of Judah
anointed him king over Israel
build a house for the Lord
smote Philistines
smitten all the host of Hadadezer
restores all the land of Saul to Mephibosheth
It was kind of difficult for me to find the accomplishments of King David. I think that this part in the Old Testament is a little harder for me to understand what is really going on.
Why did the Lord not want David to build a temple?
At first the Lord asked David to build him a temple. At that time there was a lot of bloodshed and killing going on by King David. I don't think that the Lord felt that David was in the right mind set to be building the Lord a temple after killing a bunch of people.
I am not really sure what David was going through,but if I was in a situation similar to David's in 2 Samuel 7:12-17 I will feel very grateful that the Lord wanted me to build his temple. The Lord had given David a lot of blessings and promised him a lot of good things.
David's response to God is first like who am I to do this thing for the Lord? David also says that he will do it and is praising God. I think that verse 16 is a messianic prophecy because it is sort of talking about the Messiah and all the houses and how they will be preserved and we are each from one of those houses.