So, is Ott's work infallible?
Of course not. But I don't know of any errors in his compilation. Ott's book should give your earnest search for the truth a good start.
If you want to go directly to the infallible sources you'll have to read through the decrees of the various Church Councils and dogmatic papal pronouncements which are available online. But they won't give you any information regarding the various levels of Church teaching regarding diverse subjects.