Salaam Br. miracle114,
Possibly, at the outset, the verse you are referring to is this:
Say, "I am not something original among the messengers, nor do I know what will be done with me or with you. I only follow that which is revealed to me, and I am not but a clear warner."(Qur'an, Al-Ahqaf 46:9)
In my humble opinion, firstly, the statement from which your first underlying concern comes is given as a statement to the Prophet by Allah, to profess as a response to those disbelievers who were bent on denying his message from Allah and attributing it to concoctions. In context, that would surely serve to be a humble reply considering the pressure and constant diatribe from those disbelievers. Just a no-new clear warner conveying the message as revealed (53:3-4) and unaware of what awaits him or them, being a similar fallible being. This also best captures the fact that he wouldn't have controlled what to befall him once he would have surely invented anything of what he was passing on as Qur'an, as in 46:8, which possibly partly alludes to what Allah warns in 69:44-47.
Concerning 68:3, I believe that's typical of how Allah reprieves the Prophet in the Qur'an whenever He deems apt. As a favour, he was not a madman, 68:2, and out of His favour for him, He consoles the Prophet promising him uninterrupted reward so he just was to carry on with his mission and leave whatever said about himself by those disbelievers in the hands of Allah.
In any way, this is not atypical of the Qur'an to promise the Prophet [a man approved of God (9:128), of high moral character (68:4, 33:21) and best living exemplar amongst his contemporaries (21:107)] uninterrupted reward given that any true believer who does good deeds is also promised the same great reward described by the same words. (41:8, 95:6, 84:25)
In general, as an additional reference, the prophets are collectively referred to be a party/companions with which any believer is promised to be part of, amongst those favored, as captured in the following verse.
And whoever obeys Allah and the Messenger - those will be with the ones upon whom Allah has bestowed favor of the prophets, the steadfast affirmers of truth, the martyrs and the righteous. And excellent are those as companions.(Qur'an, An-Nisa 4:69)
Hopefully that helps in some way, Insha Allah.
Regards,
Athman.