I think the answer to all of these is that if you are responding to what he wants and not assuming you know better than him what he needs, how often or for how long, then it doesn't matter awfully much. A lot of the "advice" is based on getting people who are used to hearing all about formula feeding used to how breastfeeding works. If you have a healthy baby who is showing no red flags in terms of weight or latch then there aren't really any rules because whatever you are doing is working!
He'll often pop off himself when he falls asleep but sometimes he'll fall asleep at my breast but still be nursing, at least I think he is as he still suckles. I've been popping him off and then seeing if he wants more but don't know if I'm depriving him of milk this way or not?
This is very common and ideally leaving him on the breast allows him to keep stimulating your breast to make more milk and means that if he is too tired to actively suck he may still trigger some letdowns and swallow a bit more milk. However you don't have to be a martyr to it if you need a wee, or just a break, that is OK! Some babies fall in to this "snacking" stage too early in a feed and need tickling, jostling or stripping down to make sure they actively feed, but if your LO is getting active feeding happening and everyone is happy with his weight you can leave him to it.
And if he does want more, should I be offering the same breast as I've been doing or offer the other breast?
Again if you are responding to him and feeding frequently it doesn't really matter. The advice that a baby must be allowed to "finish" a breast again is based on trying to stop people from timing feeds and switching breasts before LO is ready as this can lead to babies not getting enough milk overall. Also feeding from a breast which is actively making milk (rather than letting down milk that was made in between feeds) is likely to mean LO will get slightly fattier milk, but really all milk contains fat and as long as you aren't stopping him from feeding you can swap breasts if you like (if you feel uncomfortably engorged, need a change of position if you are sore, or if he pulls off soon after because he really was done with that first breast).
Also he seems to be fine after 1 breast at each feed so I've just been switching sides at each feed. Is this the best method as I've seen some say you should offer both breasts at each feed?
I sometimes meet women who are getting driven insane by the frequent feeding of their LO, saying "He feeds every 20 minutes" but on talking to them a bit more they also say "Oh no he's satisfied by one side at each feed, so I only offer one side". By unpicking it we realise that actually baby wants both sides but just takes a little nap in between, but mum is frustrated because she settled LO down, put her boob away started to think about napping herself, or getting herself some food and suddenly LO is crying again! This is of course very common newborn behaviour but it worries people who are used to a formula culture, so by instilling the idea that two side might be necessary we break away from the idea that breastfeeding doesn't satisfy babies. Very often newborns ARE satisfied after one side and some babies live off one side at a time till they are weaned, but others change and need both sides which is why it can be a good idea to get in to the habit of offering both so that when LO does want it they can have it. But again, unless you are planning to ignore your LO because "He's had his feed" then it doesn't really matter.
It's really hard to give answers because the advice might change depending on what is happening with LO e.g after two weeks not reaching birth weight you might have to keep LO awake to feed actively for longer and offer both sides every time, after stripping him down in between to ensure he's not too sleepy, and feed strictly every two hours or less etc. However a mum whose baby has made birth weight could ignore all this advice and go with the flow, even if it meant doing things very differently.
my baby would stay latched FOREVER if I let her. It took me about a month but I learned the difference between comfort sucking and nutritive sucking. When her swallowing slows down a lot or stops ... she's starting to suckle more because it's comforting to her.... which is good for baby sometimes she even wants to latch just to comfort herself.... 
