@Wheisler, really great questions. Lots of fun ideas to explore here. . . .
Is it possible for cardano to solve some of these problems to insure people are not using it for immoral activities?
This is a dangerous slippery slope because “immoral activities” are very subjective and rooted in a system of beliefs that may not be accepted by everyone in a given community. It’s difficult to outlaw vaguely defined “immoral activities” without controlling every aspect of a person’s existence.
Achieving an optimal balance between economic freedom, personal liberty, and a peaceful society requires trade-offs. The essence of one of those trade-offs was succinctly captured in Benjamin Franklin’s quote: “Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety.”
That same principle applies to cryptocurrencies. The only way to prevent people from doing immoral things is to unleash a morality police on society that can monitor everything we do. We already have manifestations of that today in the form of ubiquitous NSA surveillance, the political correctness police, and social justice warriors, all of which exist to control our thoughts and behavior far beyond the letter of our criminal laws. History has shown (Nazis, Mussolini’s fascists, Stalin’s NKVD/KGB, etc.) that these kinds of socially coercive tactics lead to many forms of tyranny.
How will the morality police define “morality”? How can we be sure they will be fair in their enforcement of the “morality rules”? What recourse do we have if we disagree with their definitions? How do we prevent politicians and powerful entities from using the morality police to censor us and/or block us from engaging in legitimate activities simply because they don’t like what we’re doing?
For all those reasons, the answer to your first question is: We don’t try to prevent “immoral activities” with Cardano because it is fundamentally impossible for Cardano to define and enforce morality in such a way that would be acceptable to every member of the global Cardano Community. As a result, the only thing we can do as individual citizens is to do everything reasonably possible to encourage people to live productive lives that do not infringe on the liberties and freedoms of others and let law enforcement officers enforce each nation’s laws as necessary to preserve the peace.
And what about government sanctions or terrifs?
The system of over 12,000 tariffs and non-tariff trade barriers that exists today in the U.S. is an incoherent patchwork of politically-motivated rules, taxes, and regulations that is already destructive to the global economy. For any country, Cardano can reduce the economic friction where too much friction is killing legitimate economic activity and increase economic friction where neoliberal economic policies are killing the middle class and human labor forces in many countries.
How much or how little friction is applied to a given national economy can be parameterized and adjusted according to the democratic will of each nation’s people. How that “democratic will” is determined is another use case for Cardano.
Over time, Cardano can become the governance platform upon which all national political systems are managed. With Cardano, electoral fraud, gerrymandering, and anti-democratic “winner-take-all” district elections would be abolished. When that day comes, politicians will be technically obsolete and delegative democracy will become a reality. Of course, they won’t like that; so, we can look forward to many forms of oppression and tyranny along the way.
One way or another, governments are going to want to control it and I feel like banks have enough purchasing power to ruin Bitcoin.
Yep, but fortunately, for the first time in human history, the illegitimate use of government power and corrupt laws will not be enough to stop humans from building more equitable and sustainable political and economic systems. The banks are already preparing to wage war on projects like Cardano, but the more they try to control our political and economic systems, the more people will abandon the decrepit fiat banking system and corrupt political systems that are destroying our world today. And where will they go? To Cardano Land, of course. 
What happens once Bitcoin goes to zero?
This is possible, but then Bitcoin will simply be replaced with another cryptocurrency that is more resilient to government attacks and less volatile. More importantly, over the long-run, there is a much higher probability of many major fiat currencies going to zero than gen3 cryptocurrencies like ADA going to zero.
Additionally, there are ways to create less volatile cryptocurrencies, which the Cardano team is already working on; and that will persuade many more people to abandon fiat over time. So, even if Bitcoin ever became worthless, there is very little chance that ADA will become worthless because it is based on a far stronger technical, economic, and philosophical foundation than Bitcoin or any fiat currency on Earth today.
Cardano is the Community and the Community is Cardano. Cardano will succeed to the degree that we all take ownership and contribute in whatever way we can.