The whole point of going through the halftone step is to generate something that approaches or approximates a continuous tone image when using an image setter— your digital halftone screen is used by the rip to get the dots small enough and close enough together so that it appears to be a continuous tone image when in fact it is just made up of just individual spaces between fully exposed dots.
Since there is no image setter to deal with there is no need to make a halftone pattern when printing inkjet negatives. Inkjet printers are stochastic by design (both in hardware and software), and creates a continuous tone image (print or negative) without any additional work on your part. The printers dots will be much finer than anything you introduce in photoshop, but your smooth print tones are still limited by how smooth the individual ink drops are with the OEM Epson inks. The only thing that I have found to come close enough when printing with gelatin silver is the Cone digital silver inkset. It does a much better job at smoothing out the printer dots, but there is still a small chance of ink clumping together in the really smooth areas like skies or smooth snow.