Unlikely for a condition that has lasted continuously for years to represent a disease. More likely the white film is just a good ol' "coated tongue-" drying secretions seen in dehydration-- not systemic for years on end- but local from mouth breathing or sicca syndrome (low saliva output) seen in normal aging, with rheumatoid problems or from meds. (or maybe you just talk too much?
)
The fissures were probably always there and you just never noticed them. Very deep, obvious fissures are called a "geographic tongue" and is a normal (probably genetic) variation. (BTW- in case you also just noticed them for the first time, those big bumps way back at the base of your tongue are just taste buds. They're not tumors.)
The recurring episodes of stinging on the tip of the tongue is caused by the plugging up of a saliva gland (microscopic, single units that line the whole tongue; as opposed to the big, major saliva glands like the parotid). Debris from food or sloughed off cells can plug them up and prevent the saliva from exiting, so the built up pressure is painful. They're also more likely to occur in times of local dehydration.
The yellow represents the metabolism/breakdown of DNA in the dead cells that have been laying around a while in the secretions. (Also the reason mucous turns green & yellow when you have a cold.)
Now, what I just wrote is what's
probably going on, but nobody should trust the opinion of some goof out in the Internet Cloud who has never examined you and may not even have the story right. Better see a doc. Dentists do have more experience with examining mouths, so maybe that is a good alternative choice rather than seeing another bewildered physician.