In the first episode of Parks & Rec, Ron Swanson sums himself up quite well in a talking head, when he describes himself as a libertarian.
Libertarianism is a collection of political philosophies and movements that uphold liberty as a core principle. Libertarians seek to maximize political freedom and autonomy, emphasizing freedom of choice, voluntary association, individual judgment, and self-ownership. Libertarians share a skepticism of authority and state power.
His outlook is that the government should have as little regulation as possible, and sees a majority of the things that the government does as a waste of taxpayer money. This feeds into a lot of the lifestyle choices that you have raised, so I'll address them individually:
1. Not visit hospitals and let minor issues become serious
This is the view that people should attempt to first and foremost look after themselves, so he tries to deal with his minor ailments without the help of a doctor in order to be more self-reliant. However, he understands that when an issue does become serious, he needs the expertise of a professional.
2. Believe banks are not trustable and hoard gold
He distrusts other people looking after his own money. There is the possibility of his bank collapsing, and does not trust that they can keep something that he has earned safer than he can. Even if the collapsed bank was bailed out by the government, this would be contrary to his political views of government having less oversight, so does not want to be beholden to that possibility.
It's possible that he could also be trying to minimize how much he is taxed, as he never really discloses how much gold he has or what it is worth, but he does hint that it is a lot.
3. Eat mostly meat
This is likely just because it is something he believes that men do, or maybe he just dislikes vegetables. I think this is probably less a philosophical choice, and more a personal one.
4. Believe in removing government regulation, a bar should be as unregulated as a garage sale
This is libertarianism in a nutshell. Less regulation, less government oversight, more personal freedom.
5. Sabotaging government from the inside
It seems quite hypocritical to seek to make the government smaller, and yet then go and work for the government. But really it is the most effective way for a single person to have an effect on shrinking the state. He is excited to make cuts to his own department, whereas someone who is in favor of a larger state would be reluctant to have less money to spend, so he can help to relieve the burden on the taxpayer better than someone else could.
When Chris Traeger appears in season 3, he says to Ron that his department is smaller than it should be, and he has only 7 people whereas it should have approximately 10. This is why he was such an advocate for keeping Leslie: she does the work of 3 employees, whilst only getting the wage of 1.
6. Not having normal obligations towards friends
This is part of the whole outlook of self-reliance, and voluntary association. He never feels obligated to do things for friends, as he doesn't feel like anyone should have to rely on others too much, and the only things he attends are things he either is forced to, or actually wants to.
7. Not having a mobile phone
Not sure about this one. Possibly an extension of 6: he never feels the need to be available to others as they shouldn't be relying on him, and none of his personal interests require the use of a phone.