2007 Mercedes E250 4.6L Fuel Tank Filling Issues with P0451 Code - Vent Hose or Fill Valve Diagnosis?

Hello! I've been experiencing fuel filling problems with my 2007 Mercedes E250 4.6L for the past couple of weeks. When attempting to fill the tank, the gas pump shuts off after a few seconds, and gas occasionally spits back out of the filler neck. The vehicle will accept fuel, but only at a very slow rate. After some research, I suspect either a clogged fuel vent hose or a stuck fuel fill valve. To investigate, I removed the fuel tank and inspected the accessible sections of the vent hose. I blew air through it and noticed significant resistance — however, I'm unsure if this is normal for the system. I cleaned and reassembled the vent hose and reinstalled the tank. Afterward, there was a slight improvement in filling speed, but the issue remains unresolved. Over the past few weeks, I've driven normally with no noticeable changes to engine performance, sound, or driving behavior. Yesterday morning, when starting the vehicle, the check engine light illuminated. Later that day, I took it to AutoZone for a scan and received a P045 T1 code — indicating an issue with the evaporative emissions system pressure sensor. This morning, while filling fuel, the tank now accepts gas even more slowly than before. When I removed the gas cap, I heard a long, loud hiss — which I believe is pressurized air escaping from the tank. This sound has been intermittent in the past but was noticeably longer and louder this time. Based on my research, possible causes include: 1) a clogged fuel vent hose or obstruction in the fuel tank ventilation system; 2) a stuck or partially stuck fill valve; or 3) a failing evaporative canister. The extended hiss suggests a potential blockage in the venting system, but I'm not certain. I plan to remove the fuel tank again this weekend to thoroughly inspect both the vent hose and the fill valve. While an EVAP canister replacement is possible, it's significantly more expensive and beyond my current DIY experience — especially given budget constraints. I'd appreciate any insights or tips on how to properly inspect these components during a tank removal. Any advice would be greatly appreciated! Thanks in advance!