Tamie, I am no expert. I have picked up some things as a hobbyist.
The US Army grew so fast during WWII that it was not unusual for men from one part of the country to end up in an outfit that had been originally formed from units from another part of the country, Tamie. My uncle, from Nebraska, was KIA in Italy while serving in the 34th ID, which was originally formed from Minnesota and Iowa units.
You should be able to get his personnel record (if it was not destroyed) even though you are not defined as NOK by the National Personnel Records Center (NPRC). (Their definition is, "Next-of-kin are the unremarried widow or widower, son or daughter, father or mother, brother or sister of the deceased veteran.") Info on how to do so can be found at this web page: http://www.archives.gov/st-louis/military-personnel/index.htmlhttp://www.archives.gov/st-louis/military-personnel/index.html
Do you have his serial number? It will be essential in getting his info. If not, we may be able to help you find it. If you don't have his serial number, could you tell us his name, and/or where he is buried? We might be able to help you get it online.
As for battle history, the links I gave you have pretty good unit history. In particular, follow the link "click banner to enter 121st Blue Bonnet Country" on the 8th ID site.
As for the "cactus shoulder patch", could you describe it in a bit more detail? We'll see if we can identify it.