One of my favorite things coming out of these studies is the fact that most people have an outdated mental image in their head and see themselves as smaller than they currently are. So if you have 2 large people they can both be the others fat friend.

In about the same time period I've gone from about 20 stone to about 28 stone

I've seen several of my thin friends end up heavier due to hanging out with heavier ladies at work so i'd say the idea is well founded.

Most the reputable articles I've seen claimed that since it is a matter of lifestyle the people around you the most are influenced the strongest. So if you tend to eat large portions people around you are more likely to eat more because it doesn't seem as bad. If they put on a few pounds and they have a fat friend to compare themselves to they are more likely to play it down. It really boils down to a case of "I might be bad but at least i'm not..."
Therefore, revel in your fat and gaining lifestyle and it'll make people around you fatter.

I wouldn't say dangerous, but its probably not something you want to do long term. A tablespoon of either liquid gives you 16% of your recommended saturated fat for the day, if you're using say a cup each you're looking at 500% of your recommended saturated fat before adding the nutella. So in the long run its bad for your heart, but then so is gaining.

I'd consider finding a different liquid to cut it with instead of cream if you want to use it long term. The cream and the Coconut milk are pretty comparable nutritionally so increasing one and eliminating the other won't do much aside from change the consistency.
Normally I'd make a suggestion here but I'm not familiar with coconut milk in my cooking so I'd want to experiment with it before suggesting changes.

Well if you're planning to start gaining I'd say money is always helpful. Food expenses increase the bigger you get. Luckily you can get fairly large clothes cheaply as long as you're not looking for dress clothes.
Obviously a sedentary job is preferable if you're starting to gain, but not necessary.
I'd argue that one of the best things you can do to set up for gaining is lay out your living space to minimize movement and maximize your chances to graze on snacks.

As to it being easy or hard that depends on you and your metabolism.

Generally just briefs, during winter maybe socks too. I'll wear sweatpants occasionally but they are generally too warm for me.

Well purely from a math stand point he'll need like 2000 extra calories a day to pull it off, so maybe go check out some of the gain shake recipes on here is probably a good start.

As always, i'm going to recommend a bit of moderation in junk food. Burgers may be cheap and calorie dense but all that grease is going to wreck your stomach and isn't good for you in the long run. Honestly, huge portions of what he eats now is probably the best advice.

At least 400 maybe 500 someday but i'm working on hitting 400 for now.

Generally I think what happens is that we get pretty big then decide we've gotten bigger than we wanted to be so we diet off a little. Then the diet quits producing results and we realize how much we want to eat like we used to so we gain it back. This time however it's not a matter of being way fatter than ever before so we're comfortable going even further.

Ideally during the diet phase you got yourself in better condition so it also takes longer to feel like you went too far when you start gaining again.

Personally I lost weight because i wanted to be able to take the stairs without people bringing up the shape i was in.

my workouts are generally pretty light since i'm also trying to gain, but staying in good enough shape to take the stairs cuts down on comments.

I generally do a mile or so walking a few times a week and maybe some light weight work.