I am descended from Joseph Nicklin, born 1793/94 at Cradley. At this stage it looks as if his parents were John and Elizabeth (bap 18 May 1794). Brief review of Cradley registers and IGI (which I last looked at around 1983 for this branch of my family!) suggest this John may have been baptised 25 Jan 1761 to Joseph and Mary Nicklin, but I'm sure there are other possibilities.
I am currently in touch with a descendant of Joseph Nicklin and Mary née Grovener whom he advises married at Dudley in 1740. His descent also has Mushroom (/ Musham ?) Green connections, and once the crashed Tiscali server is properly back in action and I am able to send out e-mails, hope to consolidate his more thorough 18th century research with my sketchy ideas. This does not quite tie up with your Joseph remarrying a Grace in 1750, but I am sure when I have more pieces of the jig-saw it will make sense! I'll then post any further message as appropriate.