Jeep Grand Cherokee 2004 V8 - P0301 & P0300 Misfire Codes, Cylinder Leak, and Engine Pressure Issues at 115k Miles

I took my 2004 Jeep Grand Cherokee V8 to a mechanic who diagnosed a misfire in cylinder #2. After replacing the ignition coil and five out of eight spark plugs (all found to be faulty), he suspected an electrical issue. He sent the engine control module to a specialist, who confirmed it was functioning properly. During inspection, I heard a hissing sound inside the cylinder housing—possibly indicating internal leakage. A second diagnostic scan revealed persistent P0301 and P0300 codes. The mechanic advised that engine disassembly may be necessary due to suspected mechanical failure. Notably, cylinder #1 showed only 0 psi pressure initially; after applying oil, pressure rose to 25 psi—far below the expected 125 psi for a healthy V8 engine. My check engine light remains on. I've since picked up the vehicle and am seeking a second opinion. The car has 115k miles and runs normally at highway speeds, though it sputters noticeably at idle and low speeds—worsening over time. I admit I drove it with the check engine light on for months without addressing it, becoming accustomed to the symptoms.