And also given the fact that a vast majority of them are punctuated with discretionary conditions in them, such as "what an average person would believe" or "Probable Cause" or "Credible Suspicion", etc., who is to say definitively? Afterall, the officer has sole discretion in interpretation of these conditions.

On the scene, yes. But officers have to make instant decisions with limited information then the courts get as much time as they want and as much information as they want to determine whether the officer was right or not. If an officer believes they have probable cause and uses that as the basis for a search and later a court disagrees, any evidence found in that search is inadmissible in any criminal proceeding. (Subject to certain exceptions and case law that is too detailed to go into here)

The alleged drunk driver refused a breathalyzer test at the time, which some people consider an admission of guilt. Now, I don't know if he was drunk or not, but consider this: can a police officer who lies on his police report be trusted to accurately report the breathalyzer result? (Keep in mind there's no evidence, just a number he writes down.)

There actually is evidence in many cases. The "Datamaster" breath machine used by many states prints two receipts, one for our records and one to give to the defendant that shows the results of the machine's test of its internal standard as well as the results of two separate tests of the submitted breath. Additionally, the machine logs all of the information internally and my state's crime lab can connect to the machines and download the data. (Useful in the event of a lost or torn receipt) We also video-tape the entire administrative breath testing procedure for evidence and videotape as much of the standardized field sobriety tests as is safe and practical. I imagine the same is true with competing breath machines used in some other states, though I only have direct experience with the Datamaster cdm.

In my state, the machines are actually owned by the state crime lab and they are responsible for all of their maintenance / testing, so a department couldn't rig one to print fake receipts if they wanted to.

The other issue here is that drivers slam on their breaks to avoid a ticket, which leads to more rear-end collisions. Larger vehicles often can't stop in time to make the short yellows, but smaller cars in front of them can. The small car driver slams on his or her breaks and gets rear-ended by the larger vehicle behind them. In this scenario, collisions are possible and even imminent despite both drivers behaving within the confines of the law.