Pipe Size from well to house
I lived in a house 20 years ago that had your exact installation. I lived there for 24 years and had no problem with water flow or water pressure. Since I do plumbing I thought I could improve water flow, big mistake, all that time wasted. It worked fine with or without my tinkering. The sulphur smell is probably iron. Have your water tested; Home Depot and Lowes have test kits. You take a sample and send it to a company. I would also get a second opinion from a local water softner co. Also ask your neighbors if they have the same water smell and ask how they addressed it. I had to get an iron filter and a softner from Culligan. The salesman was from the same town and had a great reputation. I was well pleased.