Most of us use the same type of fixer for film and printing, but we mix a fresh batch (from the concentrate or stock) for the printing.
Fixer from film is NOT suitable for printing because it's typically used to a much higher silver-loading, plus there are chems from the films (apparently, I know not what) that are problematic for the archival safety of the paper. Fixer from paper can be used to fix film, but you need to filter it really carefully. Paper leaves behind lots of debris that will mean you get nasty spots on your negs that never come off. Best option is to have a bottle of film-fix and a bottle of paper-fix and keep them to their separate purposes.
To the OP, you should have a read of the FAQ in my signature. People have pretty much covered the fixing-duration thing (8 mins for TMAX, no less than 5 mins if it's totally fresh) and don't forget that fixer has reduced capacity for TMAX films (about 12/L instead of 20/L).
I checked the fixer and it calls itself paper fixer but *specifically* says it's for paper and film which would be consistent with paper fixer being OK for film but not the other way around. So it sounds like I can use the fixer I had made up for the film but then mix up a fresh batch for the paper and store that in a separate container.
So are the dots in the photo showing up on the actual negatives or just in your scans? If they are in the actual negatives, I would suggest you clean the inside of camera. You should also probably take a look at the lens you used. It looks like dust has gotten on the film at some sometime in the process or it may be on the lens and thus in the negative. Or it could simply have collected on the film while it was drying.
I scan all of my negatives for archival reasons as well as for web use. The dust that I see in my scans does not show up when I go to the darkroom to actually print them. It is almost always dust on the scanner.
They are on or were on the negatives. I just took the negatives and had them party for 6min with the fixer then I washed and photo-floed them...they're drying now... I'm going to re-scan the most egregious ones and see if i fixed it. I have a rocket blower so I can give it a good dusting before I put the next roll in. I also have a kit on order that will allow me to also replace the foam by the door hinge inside that is not in great shape.
In addition to using proper agitation when fixing, it is also important to thoroughly mix the working solution. When mixing working solutions from liquid concentrates, it is easy to overlook the importance of good mixing. However, even in liquid form, standard acidic rapid fixers do not mix with water as easily as one might assume. Ilford has a very useful technical publication (on the website) which discusses this. Don't just pour the fixer concentrate into water, give a quick stir and expect it to be properly mixed. Mix it well.
I would point out, however, that I do re-use film fix (Ilford Hypam currently). I keep careful track of how many rolls I have fixed - my capacity target is about 2/3 of the manufacturer's recommendation. I monitor clearing time. I also watch out for any sediment or build up of "crud" - if any appears I stop re-using that batch.
Unlike some others, I also use HCA with film.
In short, I fix films in re-used film fix but, IMHO, I am careful and conservative about how I do so, and have the knowledge and experience that permits me to do it safely.
I'm not sure if you have this.... The fixer is good for film and paper. It's the same chemical. It may even be the same dilution. But, once the bottle of working solution in the bottle is used for one media (film or paper), it may NOT be used for the other. Mix up the fresh batch, separate them into two bottles and label them "for film" and "for paper". Then you can re-use them until they are exhausted.