The lumps you are referring to are perfectly normal for a male dog. They will appear and disappear according to his "mood". Even neutered males will display these "lumps"
Here is a good reference manual for veterinary issues.
The Merck Veterinary Manual
There is a very good section on reproduction in there.
As far as the dandruff and gas, you probably should consider changing foods. Usually with these problems, it's an intolerence or sensitivity to something in the food. I am not a big fan of adding MORE fiber to and already gassy dog. This can sometimes just make the problem worse. Dandruff can be caused by a lack of OFA's (omega fatty acids) or poor utilization of nutrients. I would recommend you add a digestive enzyme to your dogs food AND change to a less "grainy" food. Science Diet is probably (IMHO) not the best food, however many vets do recommend it. I prefer foods that have more animal protein, good ratio of OFA's, added probiotics and enzymes, and no artificial preservatives, colors, or additive's.
The addition of the digestive enzymes and probitics should help with the gas, but the OFA's will help with the skin issues.
Good luck!