Teeth have a "memory" and have the potential to move opposite of the forces that invisalign are trying to move them. Invisalign uses averages on bone density for example to determine how much each movement per tray they should move the teeth. Some people have denser bone, while others have less dense bone so some people's teeth move faster with trays. Although you should be "OK" to drop a day, it's still a risk to try to move the teeth too fast. Depending on where you are at in your treatment, some trays may only be moving a smaller number of teeth so it won't feel like much is happening. I always caution on giving the teeth more time to adjust to the movements. If teeth get moved too quickly, the roots can also resorb or become blunted. Even though its tempting to save a couple of months of treatment, you'll still need to always wear a retainer for the rest of your life so you really aren't gaining anything but increased risk in the long run. I'd also definitely speak with your dentist before making an executive decision on any of this. Hope that helps.
There isn't a problem with temporarily sealing the abutment with teflon tape for a short duration, however, a better solution would be to try to get the crown recemented as soon as possible either temporarily or permanently. The neighboring teeth and opposing teeth (on the upper arch) could shift and require the fabrication of a new crown. Also, the gums could grow around the abutment and require lasering of the tissue before they can recement the crown. I'd look for some temporary cement in a pharmacy if you don't have access to any dentists in your area. If you do have access to dentists, I'd definitely make an appointment and get the crown recemented asap.
To tell you the truth, laterals are generally shorter than centrals in a perfect dental anatomy. I honestly don't think your teeth are that far off from being where you want them. If you were to do veneers, you could stay conservative and just do the laterals, however, you may run the risk of those laterals sticking out if the teeth fade or stain over time. I would be cautious if you were to get veneers across the entire front teeth as you do have a really nice smile. Maybe a suggestion would be to start with some bondings on just the laterals to add a little length to them to see how you like it before moving into more costly procedures like veneers. You could also round the squared edges of the central incisors a little so they blend a little better with the laterals.
