"Nickel sulfamate filtering issues"

A. If you put in quite a bit, then I would start with a 15 micron bag to get the bulk of it out as quick as you can. You might even consider a 20 or 25 micron if you really have a lot of it. If it is a powder, it will clog up a low micron bag rather quickly. I would then go to a 10 micron bag which should be good enough. To be super sure that you do not risk parts, use a 1 micron bag.
If you use granular carbon, you might get away with a 10 micron to start, but remember as the bag starts to plug up, the flow rate drops significantly and does not remove as much despite the ability to reduce low micron powder.

All is not bad since the bath should be carbon treated once in a while. I preferred using carbon filter tubes with the string outside and ran it over the weekend. Does not remove as much of the organics, but it sure saved a lot of labor costs.

A. Start with five micron or more then continue filtering down to one micron. If you had some organic additives remember that they have been partially or totally removed, so you will need to replenish them.

A. If the nickel solution is in the plating tank: filter it it into a clean storage tank through a 10-15 micron filter. The filter will not remove all the carbon, but it will flow reasonable well. The continue to recycle through the filter for a few hours. Then filter back into the now cleaned plating tank through a 5 micron filter. This will remove almost all the carbon. Place a clean 5 micron filter on the plating tank and recirculate for more hours. Turnover should be several times the volume of the tank per hour, complete turn over 5 or more times per hour. The next day you should be able to add any addition agents , wetter for example, boric acid and nickel if necessary.