First and foremost, involving attorneys costs everyone a lot of time and money. Unless you want exactly that (maybe out of a desire to "punish" them), it's better to just leave.
But that's not why you need an attorney right now. Even if you're never going to file suit, an attorney will help you navigate the waters and push for the best possible outcome in your situation. Maybe that's compensation for a clean exit, or simply putting an outright stop to the CTO's machinations. I don't know.
Yes, they cost money. But this is already a legal matter. It became one the moment the CTO started to try and squeeze the OP out. Spending the money on an attorney now is simply an attempt to avoid losing more money later on down the road.
Not talking to an attorney at this point is nothing short of willful ignorance. It won't stop the squeeze-out, nor will being able to say "I didn't bring in the lawyers!" somehow make things all better when you're out the door, up the creek, and without the stupid fucking paddle.
1. Negotiations
2. Understanding the legal situation
Regarding the second point, the correct advice is not to sign contracts whose consequences you do not understand. Regarding the first point, engaging a lawyer will destroy whatever trust and mutual understanding is left in the relationship between the founders.
This might be the US way of doing things. But before telling someone to hire a lawyer, you should make sure that the case in question is not taking place in a country where doing this is generally taken as a big offense.
Ideally, yes, but it sounds like that ship sailed already.
Regarding the first point, engaging a lawyer will destroy whatever trust and mutual understanding is left in the relationship between the founders.
You don't have to tell them you hired a lawyer at first, when you're just looking for some basic advice about what your situation really is.
If it goes further and your lawyer is actively representing you when dealing with other people in a business context, and those other people take offence at this or it destroys trust, then you never really had a worthwhile relationship with them to begin with and you definitely want a lawyer in your corner.
Interesting. Can you give an example of such a place, and how things tend to work there? What would be your advice to the founder if they were in that country?
What I find disgusting is the culture of hiring a lawyer to put as many traps as possible into a contract, which forces the other party to hire another lawyer to remove the traps again. This does not make anyone better off except for the lawyers.
Healthy and lasting business relationships are built on trust. The relationship between McDonald's and Coca-Cola is based on a simple hand-shake. If you want to preserve such a relationship and it comes to a disagreement, the first thing you should do is talking to each other. Once that fails, you can consult the lawyer - which will formalize everything and slow the process down (e.g. "I cannot disuss this today because I have to check with my lawyer first"). And being slow is one of the things one should avoid when being in a startup.
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Look there is no reasonable discourse possible with idiocy like this. If you think a sustainable business is possible without covering your legal grounds, I'm wondering if you'd be interested in this bridge in Brooklyn I have for sale. Blanket statements like 'the US spends a much higher share of its GDP on lawyers' don't mean a thing without a proper understanding of the legal system, business culture etc. It is obvious from your postings in this thread you know nothing about what lawyers actually do for a business, in the US nor in Germany, and that your statements are based on what you see on TV and blind prejudices.
(disclaimers: I have a law degree but have never practiced. I'm not an American, yet I have spend amounts on lawyers the last years that you probably feel are obscene, and this in a country that is considered similar to Germany in its look on lawyers, and they were worth every penny, and then some. I have also paid dearly in the past for not doing things the formal legal way, including in Germany.)
The money you save hiring a good lawyer almost always justifies the money spent, especially in a situation where you have forces mounted against you.
Not only can they help you with "do this, don't do that" advice, they are very strategic in positioning and can offer incredible advice based on years of experience.
Good lawyers generally see situations on both sides of the coin because they have clients on both sides of the coin, and hiring one can give you volumes of insight and perspective. Will it cost you $5K? Yes, but that $5K now might get you $8M two years from now...