Welcome to keto. Not sure what your situation (age, weight, conditions, continent, etc.) or goals (weight loss, chronic disease reversal, prevention, longevity, etc.) are which will help in any more meaningful advice in the future but here goes.
BPC - for most it’s fine with sweetener but sweet-n-low is one of the least preferred. Some people find caffeine is an issue on keto, some find sweeteners kick them out of ketosis so you will need to experiment. Keep up your coffee/cream/sweetener (maybe try stevia/swerve) and if you are not succeeding, the coffee or the sweetener to both may be something to cut out.
App - three main ones, many others. Get them for free (mobile and web) and see what you prefer. All are functional for free but have additional features to pay for on subscription. I use LoseIt, many use MyFitnessPal or Cronometer. There are plenty of others with a purer keto focus (e.g. KetoDiet) but they have deficiencies vs. the more general ones.
Sauces - check the labels. Many are full of hidden carbs so probably no-go but there may be reduced/sugar free versions e.g. reduced sugar ketchup or sugar free BBQ sauce. You can also make your own with lots of keto recipes online.
You will see ketosis in strips at the beginning or just stick to 20g net carbs and your are pretty sure to be guaranteed in ketosis in a few days. Remember, ketosis is NOT the goal, it’s the means to the end of fat adaptation (takes several to many weeks) so many ketonians never measure ketosis and trust their diet. I have never measured my ketones and don’t care to. There isn’t much to be learned by the levels of ketones, especially when urine/breath ketones are the wasted ones not the used ones.
Drinking - alcohol is processed by the liver above all since it is a toxin so it will slow/stall ketosis for a short time but isn’t the end of the world. The Cranberry juice on the other hand is probably out - find sugar free.
Weight loss is a symptom of metabolic healing so while you’ll lose some water weight at first, be patient. Some lose loads of weight in the first few days and weeks, some take a couple of month to lose. Focus on the healing and weight loss will come.