I am personally not convinced that experiences from the PTO service of B-29 can be extrapolated to europe, particularely the latter part, say from feb. 45 to august 45.
Tactics were simply to different there. In order to allow precise bombardement, the B-29 had to fly comparably low for most of the mission, something which was eased by the airspace condition (approach to and return from destiny was over empty ocean and not enemy (better: contested) airspace. The remote gunnery system usually was removed from the B-29 A and -B during this period, leaving the tail guns only. Another important tactical difference lies in the formation flying. Over Japan, there wasn´t exactly any kind of a tight formation flying with single or pairs of B-29 operating independently, this was forced by the long range requirement (air assembly of large formations is a long lasting and fuel gulping task).
Things in europe would differ greatly:
1.) It is not reasonable that B-29 would operate at low altitude as they did in Japan. That would be negative here over contested airspace (lots of Flak, too.) and it isn´t necessary due to the generally shorter ranges.
2.) It is not reasonable with the tight AAA concentration and the proposed Luftwaffe interceptor capabilities (both night and day) that the B-29 would remove their remote gunnery system.
3.) The higher range tolerances would allow the assembly of large formations prior to entering contested airspace at least in daylight operations (open formations would remain in night sorties).
These differences will have both, tactical and logistical consequences:
A1.) The formations, flying higher and equipped better will become increasingly difficult to attack with means of conventional airplanes, esspeccially LW nightfighters (barring the few Ju-388J) and old 8.8cm AAA, thus the number of losses should be expected to proportionally reduce compared to B-17/B-24 raids.
A2.) As a direct reaction to A1.) - we would have to admit the possibility that the Luftwaffe transformes it´s bomber hunter Fw-190 groups into bomber hunter Me-262 groups more rapidly than historically. It is also reasonable that the AAA concentrates their advanced 8.8cm Flak 41 over key targets as we would expect means to extend their effective AAA ceiling. I even wouldn´t rule out that the high altitude mission profile of the B-29 would force the mass production of SAM, which was rejected in exactly this timeframe. None of these countermeasures would develop a notable effect until april 45 but they would give an uncomfortable prospect to future operations.
B1.) The number of B-29 accidents would increase substantially compared to B-17/B-24 raids (conditions comparable to the early, say 1944 period of the B-29 operations vs. Japan), mostly due to engine overheating problems.
B2.) As a direct result to B1.) adaequate cooling techniques would be developed as they were historically.
C1.) The high altitude mission envelope would confront the bombing crews with the jet stream, making navigational issues more problematic and precise bombardements more a matter of luck than anything else (this problem was encountered over Japan, too and was adressed with the low altitude mission profile, which followed from feb. 45 onwards).
C2.) As a direct result of C1.) the altitude mission profile would have been lowered somehow, but not as deep as it was done over japan. A normal high altitude mission profile (at around 20.000-25.000 ft.) would have been accepted for the bombing run.
It can go different ways but I suspect that fractionally more B-29 would return than B-24/B-17 for each given mission.
The Luftwaffe interceptor capabilities for the timeframe in question are a bit overstated - little would change. The Fw-190 Sturmgruppen are to slow and couldn´t operate high enough to play a role while the Me-262 could still get in for the shot. I expect that most high altitude interceptions indeed would result from the jets say from mid feb. 45 onwards with little change to historical loss ratios which were low for the bombers and high for the interceptors in this timeframe!