Oh, sorry - I see Pet battles in the title, but New Player in the menu. Odd. Web glitch,I presume.
OK, I see one or two misunderstandings here.
You don’t need Chromie Time, and if I were doing this, I would avoid it like the plague. If your character was in Chromie Time, I suggest you go to her and ask her to return to the current timeline. That will get you out of it, and into the natural state of the zones.
But even if you do stay in Chromie Time, you will not gain levels much beyond 30 unless you are getting XP from something like gathering or pets or archaeology. You might get as far as 35-36 before you stop levelling, but no more than that. Since the mobs are oinly up ro 30, and t6he quests are up to 30, a level 33 will be looking at single-digit XP from quests, at most, and no XP from mob kills.
Technically, there is no level at which you cannot take breadcrumb quests. You can pick up a pointer to Silverpine at level 80. However, you will get offered so many breadcrumbs before you get Silverpine that it becomes impractical, This is a problem, and Blizzard should fix it, but I doubt that they will.
However, you do not need Breadcrumbs. They don’t do anything for you except give you a place to start in the zone. You could use an addon like BTWQuests, or just look up Wowhead, to find a place to start.
If you want to level as high as possible while staying in Chromie Time (and I do not believe that is necessary or desirable) than the answer is 67. After 67, Chromie time is no longer available:
The option to choose a Timewalking Campaign from Chromie will be removed automatically upon reaching level 68 or upon entering your faction’s main city while level 70, whichever comes first.