I have a 1956 Singer 99K, it has no problem sewing the fabrics you mentioned. Perhaps it’s not threaded quite right?
I downloaded the user manual from the internet and found in the beginning I was threading one step backwards- it wasn’t sewing correctly. Also make sure the bobbin is in correctly. I’ve never used upholstery thread- I would try regular cotton or polyester thread & see if that makes a difference. I use Aurifil thread without problems