Unfortunately, in the USA this is a very slippery slope. The most difficult part of navigating these laws is they vary greatly state by state, in a few states it would be completely legal to offer online real-money gambling (with a license). There are federal laws as well, and I would suggest you get familiar with these laws and call your states gaming commission as well as try to get ahold of any federal office that would handle gaming. It surprised me that I was able to get a hold of someone for a question related to a poker club I ran in my state of California to ask a specific question about what I could/could not do related to playing poker within the club.
I will assume you offer this app/platform to all USA customers and will give my thoughts based on my experiences with these laws keeping that in mind.
Yes, as far as I know this is legal, as there are other play money poker sites/apps out there that are available. You may want to check with a lawyer or gaming commission to see if any disclaimers/legal requirements are needed in order to operate such a platform.
This I would stay away from, as I know there are ways of getting around the wire act like using cryptocurrency. Although the wire act is technically circumvented here, I am aware that there are issues with hosting online poker within the US. This is why popular online poker sites in the US like Americas Cardroom are based in Costa Rica, to avoid any issues this may cause. I would look into it further but if other sites do not operate out of the US then it is likely that you will not be able to operate your site out of the US.
This is an interesting question, many states allow home games that do not take rake and are held within private residences, but many others do not. Federally, it could be allowed but it would require some digging on your part. The main issue is that it is an online service and those generally are not considered home games if they are operated from a central server.
Yes, assuming you meet all of the legal requirements that other applications on the app store meet then this should not be an issue, as there are other sites/apps that do this already within the US.
I believe this would be legal, but I would again check the laws and ask questions before you do anything.
Main idea here is that it is not black and white, checking the federal/local laws is required to guarantee that you can operate safely. There are gaming lawyers that specialize in this kind of law if you are in the position to spend some money.
Using bitcoin is good/bad, it is good because it is untraceable and circumvents the wire act and other laws that prevent real money gaming, but it is bad because using bitcoin raises suspicion, you could be doing illegal things in the background and the law-enforcers have no way of knowing and you could be shut down because of that.
Look into what other apps are doing (WSOP app, pokerbros, pokerrrr, pokerstars.net, etc.) and call the agencies responsible for poker and gambling within the US to make sure what you are planning on doing is legal.