Tome of Learning won't do anything for your Reaper XP so don't bother with #1 to 're-enable' your ToL. There is also a 'bug' where quests run in Heroic lose Tome of Learning first time bonus if you run them again in Epic/Legendary. But again that won't matter from a Reaper XP point of view.
The only way to do it more efficiently is do as many quests as you can as high reaper at least once, then TR. Then level back to 20+ either with an Otto's, or if you don't have one, level up normally running as high reaper as you can quickly.
Rinse and repeat.
The Heroic Reaper XP is small compared to high end, but its pretty much free if you have to level anyway. If you can handle R4 or higher, it really does add up but if your build doesn't level quickly or is a 'late bloomer' you might want to avoid spending extra time doing higher reapers.
The fastest way is to do this process with a buddy or five, if you can convince someone who plays the same sort of hours as you to jump on the train too.
If you are soloing, keep an eye out for PUG's. Most times you will complete quests in half the time with even semi competent team mates.
The last points will not be quick though. If your goal is to get them and then stop playing, you might save yourself some trouble and do it the other way around.