Sorry to hear that he is having some issues with the pocket, I had a pacemaker for about 10 years and didn't have that particular issue. But wanted to at least say the fact they are looking into it, and being in the hospital should be beneficial to keep a close eye on it as they solve the issue. I'm not a doctor but from my experience and the fact he was on blood thinners may have slowed the healing process. I remember with mine there was strick instructions to not get the area too wet, no showers for the first 6 weeks, baths only. No lifting my arms over my head ,and as it sounds like was done, report any unusual swelling.
You mentioned Boston Technology and I'm wondering if that was the same company mine was , when mine was installed it was Boston Scientific. Great pacemaker and never had any issues with mine from an operational standpoint pluss the tech that programmed it were very knowledgeable.
So, Please let me know if I can help further? I ended up myself needing a heart transplant as my heart got worse but not because of the pacemaker. Mine saved my life many times.