Is swearing a written oath of divorce online considered an oath, and if so, is it permissible to use a webcam after meeting the wife, knowing that the oath was not to see her via webcam until meeting her, and that the marriage has not yet been consummated?

An oath of divorce written online is a metaphorical expression (kinayah) and does not take effect unless intended. If you did not intend it, then nothing is binding on you. If you intended divorce upon seeing your wife via camera for a certain period that ends with you joining her, then the divorce does not take effect if you see her via camera after you have joined her, because an oath is based on the intention of the one who swears it. However, if the viewing occurred between you before you joined your wife, then the divorce is considered effective. A wife who is legally contracted is subject to divorce, and it becomes an irrevocable divorce (bain) before consummation or valid seclusion.