In answer to your question, yes, resoundingly, many on these forums have been in your partner's situation and have fully recovered and gone on to live their lives, return to their jobs, and attain health and peace of mind.
I was diagnosed in hospital with PCP and CD4's of nine (Viral Load of 110,000). My oxygen saturation at the time was similar to your partner's. I was back at work fulltime in about a month. Today's medication is miraculous and the so-called Lazarus Effect is quite common:
It sounds like your partner has already improved markedly, since he no longer is in the Intensive Care Unit, but now on a "regular" floor. You have every reason to be very hopeful and be optimistic of his full recovery.
Most likely he will be started on antiretroviral medication immediately and some prophylactics to make sure he doesn't get pneumocystis pneumonia (PCP) again (Bactrim or the equivalent) until his CD4's are safely above 200 and azithromycin to guard against the opportunistic infection of Myobacterium-Avium-Complex (MAC) until his CD4's are safely above 100:
It may take a while for his CD4's to recover to a safe threshold (above 200), but the goal now is to get his viral load to an "undetectable" state so his CD4's can begin to recover.
As long as your partner is adherent to his new medical regimen, you and he have long and healthy lives ahead of you. Best wishes to you both as you begin the journey back to health.
Please use these forums for continued support and tell your partner to feel free to seek the support he may need here, too.
We all here look forward to updates from you on his continuing progress.