So it looks like that fork is threaded so it is not designed for a threadless stem and the threadless stem is not going to get the support it needs being run on those threads and the bearings weren't mean to be crammed on top of a stem. I think you just need to face the facts you need a proper threadless steerer tube so probably a new fork or just use the fork properly and get a quill adaptor as shown by Camilo . It looks like from your photos you have a threadless stem with a headset so not sure why you wouldn't use that one. My guess is both are of equal quality and probably equally worn out but I would rather have the proper fork for the stem I want to run rather than trying to run things dangerously because???

SR Suntour makes some pretty cheap 1 1/8" threadless forks that would give you similar suspension qualities but in a new fork that will work with your stem or if you have a co-op nearby you could get something there or get a Sunlite or MSW/Dimension threadless steel for for like $80-100 and call it a day.