Can I file for ssi/disability if I can't stand any longer than 30 minutes due to back pain and have copd?

Yes. An evaluation will be done to determine if you meet criteria for SSI based on your limitations and objective health data.
Probably. You can always file weather they approve is up to them but people with fewer linitsxare on SSI right now there are large regional differences in acceptance rates.
Pulmonary criteria. From the lung perspective they will ask for a pulmonary function test. If the fev1 is less than one, then you would qualify. Other factors include use of oxygen, and not beeing able to walk more than 200 feet. Your doctor will need to document that you are no longer able to do your job. You also need to explain why you cannot have a "desk" job.