I’ve never had a bearing that tight on the shaft. They usually slide off once the collar is off. Any pressure on the bearing has to be on the center sleeve only or you risk ruining it. You might be able to get a flat blades screwdriver between the inner sleeve and the bit body and rotate it to get the bearing moving. Be careful to stay away from the carbide if you do that.
As for cleaning it, there isn’t anything to clean but the outer surface. If the bearing needs lubricating I use a product from Lee Valley in a small spray can. I think it’s called Dry Lube. It will flow into the bearing. It has freed up bearings on laminate trimmers for me which is the bit that gives me the most trouble with bearings getting sticky and making growling noises. White side sells replacement bearings if it needs it.
The collar held the bearing in place against a stop machined into the body of the bit. Put some penetrating oil on the shaft and let is soak. Then put the bit in a vise and gently tap the top of the bit with a dead blow malet. Do not grip the bit with the vice but have the bearing on top of the jaws so the bit is suspended by the bearing. Watch out when the bearing breaks the bit can fall to the floor. The bearing will most likely have a marking identifying it. You should replace the bearing. If the bearing is not marked then you know it is a 1/2 inch ID and just measure the outside ID and look it up.