SMG, giving him oxygen he doesn't need (a pulse ox of 93-94 isn't) could make things worse...do his docs, esp. the lead, know ALS? Don't be afraid to ask for someone who does. Don't be passive.
I know you're scared, but from what you've said, things could be very far from the end. We just need more info to be more definitive about saying anything about that, and you deserve more info than what you have. Make it clear that you want to know all the evidence at hand and that he wants only the treatment that is relevant to his current complication.
Be clear about his choices. Make sure while he can talk or nod or whatever that someone charts his agreement that you will speak for him, if you do not have paperwork to that effect.
You can walk out any time, he can refuse any medication or intervention any time. If they started abx before the film was read (which takes a couple of seconds), ask what the reasoning is and what he is getting. What did they hear when they listened to his lungs & heart?
If he doesn't want a trach or vent, and I haven't heard any reason why he would need one anyway, he absolutely does not even have to discuss that. It is just their obligation to make recommendations and to state consequences for anything that you put off/decide against/wait to see results.
If he's been coughing (fever?) for a month, and his need for the BiPAP has not increased dramatically during that time, he likely has bronchitis or pneumonia. If he's been eating, drinking, or using his feeding tube regularly, he could be well-equipped to fight it off, with a little help.
Stay with him -- stay alert. Pretend that every time someone wants to do something or administer something that they came up to you in the street -- be that skeptical. I will PM you my contact info in case you need anything off line.
--Laurie