I have been doing the 16/8 split for about a week, and I can got the 16 hours without eating just fine, but as soon as I start eating I seem to lose my self control and eat whatever I want. So I was thinking of doing a fast for days at a time as I have seen quite a few posts about it. My ultimate goal is weight loss.

Have you tried a ketogenic style diet? Reducing food palate-ability also helps greatly but it helps to have some loose guidelines to follow beforehand.

I keep seeing "water fast" as a description, does that mean all you are consuming is water? If so, how long can you do that safely before your body needs something else? I was thinking of starting with a 24 hour fast and then slowly increasing the days from there.

Yes, people on this forum fast from days to weeks to months, most supplementing some form of electrolytes.

How often can you do an extended fast? For example, if I did a 3 day fast this week, could I do another one next week? Or if I did a longer 7 day fast, how long should I wait before doing it again? If I do an extended fast and get super hungry on like day 3 of 7 should I break the fast and start over or is it ok to consume a small amount of calories?

Its relative to the health of the individual and nutrient density of their current diet. I think it is more important to establish healthy eating habits before concerning yourself over how long you should be fasting. That being said I personally fast several days every week and usually a 1 week fast every month. I'm sure I would be fine with more frequent fasts but this depends largely on activity level.

I keep seeing talk about salt and electrolytes, can you elaborate on what those are for? Do they help with the hunger or are they more for helping you stay hydrated?

Most people consume sodium out of balance in comparison to other minerals. When fasting this past consumption of excess sodium becomes apparent. You can either supplement the extra electrolytes your body is used to or feel like shit for a few days to get through the low energy levels. I drink a high mineral water but don't supplement and specific electrolytes.

I don't work a normal desk job, I do sit sometimes, but I take anywhere from 12-14k steps a day, and I have started working out again, is it out to fast with that much physical activity? I usually have a protein shake after I work out, should I not do that on a fast?

In my experience energy levels rely on sleep and recovery when fasting. If you don't sleep too well one might you may have a really weak workout but if you sleep well its likely you might have a workout equivalent to one when you weren't fasting.