I am now able to get more urine from the tip. However, when I urinate I can feel uncomfortable pressure where the vagina used to open. Then the large amount of urine is leaking out of the tip for several hours after urinating. My doctor thinks there is an internal fistula as well. It seems as if it is emptying into where the vaginal cavity used to be and then coming out. Should I still just continue on with urination through urethra?

Yes, continue to void and after urination please press gently the area of former vagina to empty all the rest of urine. Collection will be smaller and smaller. Why? You have now very long channel that is artificial tube without muscle support like in male urethra. For this reason you need to use abdominal muscle pressure to press the bladder additionally and to give support for complete emptying. Some urine stays into the whole urethra and you have to press it in the midline from the bottom to the top to empty the tube completely and to prevent postvoiding leakage and drops.