1)
Did Shidafon and Yerakon strike them themselves?
1.
Radak: It struck the work of their hands. Also "v'Osanu Al Timrodu" (Yehoshua 22:19) is like u'Vanu.
2)
Why does it say "v'Ein Eschem Elai"?
1.
Radak #1: With all this, you yourselves are not to Me. Also "Yavi Oso" (Bamidbar 6:13) and "va'Yir'u ha'Ro'im 1 " (Yechezkel 34:8)
2.
Radak #2: I do not see you returning to Me.
3.
Malbim: Only your hands' actions were to Me, but not you yourselves. I.e. you did external acts without intent - a body without a Neshamah, a Mikdash of rocks without hearts. Therefore I sent a curse in your hands' actions!
1
These verses mean that he brings himself, and they grazed themselves. (PF).