The CPS operates a two part test when considering whether to prosecute. Firstly they must ensure that there is evidence to support a reasonable chance of conviction. That is certainly ensured here. By your own admission you assaulted your husband and it was committed in a domestic situation which aggravates the matter considerably.
Then they must examine whether a prosecution is in the “public interest”. The CPS takes a very serious view of any domestic violence incidence (for that is what this is). Furthermore, they will usually persist with a prosecution wherever possible even if the alleged victim withdraws their co-operation. Contrarily to your contention that to prosecute you is not in the public interest, the CPS would argue that not to do so is against the public interest.
Your argument about the sergeant’s lack of proper procedure is not a consideration in this matter and the “public interest” test does not involve ignoring comparatively trivial offences in preference to those more serious. Regretfully, as has been said, you should have accepted the caution because your guilt is beyond argument. As has been said, you may be able to persuade the Bench that this was an isolated incident unlikely to be repeated and you may receive a Conditional Discharge. However, you will appear in a specific Domestic Violence court where all cases such as this are viewed with some seriousness.