Mike Ehrmentraut's granddaughter Kaylee is clearly the same age as she will be during the run of Breaking Bad. SInce Better Call Saul is a prequel to that series, this should not be the case.
Hector Salamanca's "plan" to keep his nephew out of prison makes little sense. Even if Mike were to claim that he was the one who brought the gun, Tuco is stated to be a felon and thus cannot be in possession of a firearm legally for any reason. His sentence would still be significant regardless of Mike's testimony, especially if his prior crimes were violent.
Additionally, the federal government has often stepped in to prosecute drug offenders who are caught with weapons. Given the fact that the ABQ police know Tuco to be a serious player in the local drug scene as well as a violent ex-con, they might be just as likely to turn his prosecution over to the feds as they are to lower the charges against him.
In some of the wide shots of throughout the series, it's clear that the Albuquerque is the one that exists from 2015 and later rather the one which existed in the early 2000s. There are homes in areas which were vacant in 2003 and there buildings missing which have been torn down in the interim.
In the episode where Mike recalls moving to Albuquerque, he arrives on the Roadrunner Rail line. However the train did not exist at that time.