335 timings are an issue especially leaving Killingworth off memory serves leaves a minute or two after 342 to Wallsend and in turn is a quicker service via Forest Hall to Asda and station Road /Mullen Road Shops

With regards to extending 335 to Holystone I would look at extending the 351 from Holystone to Northumberland Park even on an evening

I would change the 335 after quarom and go via the old route past the station pub and over the level crossing then round Killingworth loop (anti clockwise so it goes via the school into Killingworth bus station) it also creates a link for camperdown and Burradon industrial estates