>>>He is pleading not guilty and he thinks he is going to get away with it and the charges dropped. What is the likely hood of this happening
Nil
>>>And what happens now he answers bail on the 28th February, although he is due to fly to Portugal Tuesday
Standard bail conditions do NOT prevent a person leaving the country but if fails to answer bail at the designated time he will have committed a criminal offence by doing so. (That applies even if the person is later found not guilty of any other offence or has all charges dropped). So if your ex is out of the country when he should be answering bail he will be arrested upon his return and probably held in prison until his trial.
If your ex does answer bail at the specified date and time he might well be simply re-bailed. Such cases usually take well over a year to get to court (with 15 to 18 months being common).
>>>how long of a sentence is he looking at
Your description of the events seems to rule out any possibility of it being classed as a 'Category 3' offence (which is the least serious level). It will probably be classed as 'Category 2', which has a 'starting point' sentence of 6 years imprisonment, with a range of 5 to 9 years available to the judge:
http://www.sentencingcouncil.org.uk/wp-content/uploads/Assault_definitive_guideline_-_Crown_Court.pdf
(See pages 3 to 6).