Practicing the exercise for 4th finger will not cause harm or bad habit. It is a good muscle strengthening exercise for pinkie. I did not see a (picture 1) but I think it is probably a pic of the collapsed pinkie on the fingerboard. This is a very common issue, I have it myself. It is a result of having a double jointed knuckle. It can be overcome. Violin Tutor Pro recently posted an article from Violinist.com on facebook about this. One thing I read was the main cause of the pinkie sitting straight instead of rounded is that the player drops the pinkie from the first knuckle (closest) to the palm. But there is another knuckle lower in the hand, and if you think of dropping the pinkie from that joint, keeping the hand turned toward the fingerboard and staying close as you can to the fingerboard, you will have a better chance of achieving a rounded pinkie.
In answer to 2, 3, and 4. All good things, with time. You are aware and such a good student. You will work on all these things eventually.
I will check the PDF, but I don’t want to click that link and lose my post until I read yours and answer all. I will check after and confirm.
The Wohlfahrt (I always spell this wrong) that you are working on, do the next one in the book. Do them in order. I would be happy to listen to them all. If you have worked through that book let me know. I can select the next etude book. Meanwhile, Sevcik is heavily finger exercises at the beginning. Repeat the finger patters and play them in tune and fast. They are good for warm ups.
There are also Schradieck technique books you will want to do. But Sevick first and then you will fly through Book 1.
I hope to know your name some day, as I write her to you and often want to refer to you as something other than nguyenthienchan 🙂 But thank you for sharing your history with me. Your hope to play the greats is so beautiful and I want to tell you that you CAN be a very accomplished violinist. You have an excellent start. (and now, an excellent online teacher *smiles*) If it is true that some inherent talent is required to get there, I confirm, you have it. I personally believe that every person can learn and that talent is earned, not bestowed from a higher power. For every person, it takes time, hard work, and good training. Every great violinist you admire has suffered the self doubt and seriousness, the stress of practice over years and years to achieve their skills. No one wakes up one day and plays violin with mastery. We all take each step to reach the next goal.
I am always here when you have questions. Remember this. It’s not what you play, but how you play it. 🙂 Talk soon. I will check PDF and post again.