2001 Toyota Camry 3.0 engine. Low compression all cylinders.

Bought this car being sold with seized engine. First step was to verify. Used breaker bar and socket to turn engine by hand, would not turn. Then I used leg power on breaker bar and was able to turn engine. Was hard tuning first 180 degrees then became easy and can now do with arm power. Starter is able turn engine (did not try starter until after broke free). Did a compression test on cylinders 2,4,5,6 all read ~30 psi. Performed compression test with throttles open. Checked timing belt. Sticker says it was replaced at 175000 miles (car has 187000 miles now). Belt and water pump looked newish. Timing marks line up. Other symptom is no communication through OBD2 connector. 2 different readers could not connect. Suggestions on next steps? Considering taking valve cover off to inspect cam .

Update- Pulled left side valve cover. Both cams dots line up. Introduce air into cylinder 2, came out cylinder 4 spark plug hole. Air into cyl 4 came out cyl 2 and 6 spark plug hole. Air into cyl 6 came out throttle plate . I made sure each cylinder had valves closed. Air into cyl 5 came out throttle plate (I noticed after introducing air that oil was coming out of throttle plate). I am thinking both head gaskets are blown or heads are warp. Any comments on low compression, did I miss something?
Where to start on no coms through OBD2 connector? OBD2 powers scanner. I would like to diagnose this before any engine disassembly.
Don't know what caused engine seize before breaking loose and started to rotate. How could this be related to other issues?

Does sound like blown head gaskets, i think you are on the right track.
What scan tool did you use?
some cheap scanners won't read early toyota's.

Self sabotage on the no coms with ECM. I had removed the fuse for EFI before doing compression tests. ECM shares that that fuse.