That's what Ruhollah and I were trying to figure out. I would guess it is made in North Korea but it looks quite similar (both in general appearance and wheel arrangement) to the MAZ-547 which is used to carry most of Russia's road-mobile ICBMs. I posted a pic earlier of a MAZ-547 variant that has a nearly identical wheel arrangement to the Musudan's TEL.
As to the warhead design. Indeed there are some similarities between the Musudan/R-27 warhead design and the Shahab-3/Sejil warhead. Where Iran/North Korea got the idea to design such a warhead I dont know but there are a few things to remember about the R-27 for which the Musudan is believed to be based. It only has a warhead of 650kg and was designed solely for the carrying of nuclear warheads. IF Iran were to pursue a nuclear weapon its unlikely the smaller Shahab-3/Ghadr-1 warhead wouldn't be able to carry a proper nuclear warhead since history shows most 1st generation nuclear warheads are not very compact (with exception to gun-types designs) so its unlikely the Shahab-3/Ghadr-1 warhead was designed with a nuclear warhead in mind so logically from its shape I would assume its for penetration-type attacks.