I cannot read the name of Johann Henrich Illart's father from either his baptism nor his burial record. It looks like "S__ndal" to my eye, and if I'm reading it right, it shows him as being a "Ackerknecht" (farmhand) from Mihla. I have recorded the names and family tree of every Illart/Illert who should have been alive in Mihla at the time, but cannot match that pattern to any name.
The first name you are looking for is Wendel. You can find each letter elsewhere: W in Wilhelm (at the top), e and n for example in begraben (right next to the name), d and l in Kindlein (line below).
The last name though is almost certainly Iffart, not Illart, so probably not related to the Illerts you have recently been looking at. Your reading of Ackerknecht as the occupation is correct.