@Synycalwon... The Block Knox and OTA is only for Kitkat. I don't think they updated it to run on LP. To fend off OTA, the files that need to be blocked are...
com.samsung.sdm"
com.policydm"
To the OP... At one time, Package Disabler Pro may have been able to block these, but they may have changed the app... there's a vague memory about something that was changed. In any case, see if the app has the above listed items as blockable... if so, block them. Also, OTA's are downloaded to the system cache before being installed, so what you should do is block the listed items, then enter recovery, and wipe the system cache.
Note... the above is only for blocking OTA. If you also want to block Knox, then there are other items that need to be blocked. Let us know if this is what you want to do.