19 days should be well enough to ferment and condition. 1.018 is not a great FG for an amber - but it is close. 1.010 – 1.015 is the range. You might try raising the temp up to 73 or so for another few days, and maybe rocking or swirling the carboy a little bit to rouse the yeast. Did you do an appropriate size starter? How about the oxygen. Maybe next time - a bit bigger on the starter. You should be fine, though. Don't worry.
You now have two choices for carbonation. You can keg condition (at room temp) by making up a sterile corn sugar solution and racking on top of it. There are a few online calculators for determining the right amount of sugar. Problem is that the first pint will be all yeast. Or, you can force carb it. If you decide the latter, I would crash it down to serving temp in the carboy - then rack. Remember when the beer cools, the pressure inside will drop (and suck the airlock liquid into the beer). Whenever I cool, I revert to sanitized aluminum foil. Then it is just temperature and pressure. For an amber, I would say about 2.4 volumes is good. The online tools will probably have a tool for force carbing too. It will be around 12 PSI at 40 degrees. You can just set it for 12 and wait the week or so, or you can shake it. I do a hybrid. I shake it for a bit at a higher pressure, then slowly move it down - making sure by the end I can still hear gas going in around 12. Then it's ready in a day or two.
As far as a good racking method to a keg: Fill your keg up completely with starsan (5 gal), purge the headspace, and put it on a bathroom scale to determine the 'full weight'. Shake it up a bit, then push it all out with CO2. Then hook up a liquid disconnect to your racking hose on your sterile siphon. Bleed off all the pressure and twist your pressure relief valve to stay open. Then (and only then

), hook up your disconnect and start your sterile siphon. Stop the flow by closing the PRV, and lifting the siphon out of the beer. Purge the headspace of the fresh keg. Spray some starsan on the posts. Then start your carbing method of choice.
Mylo
Mylo