BW
hope you little man gets better soon
My DS has chronic lung disease and been on a few nite rides to the hossy for chest related illness. His o2 levels on a good day hover around 93 so be reassured that if his O2 levels were OK, then that is really good!!! All the girls have given you good advice about keeping fluids up etc.

As for dx asthma- the only way they really can dx it is if they respond to ventolin and there is no other cause for breathlessness. I went one nite to hossy as trouble breathing with DS - thought it was pnumonia again and chest was clear- they gave him ventolin, predisilone and he has been asthmatic ever since. He was 3 years old then.
If he is still struggling, try the good ole hot shower with him in the same room to inhale the steam- works well, as well as hitting his back to try and break up the phlem.
take care hun