1. How to Chen Yu himself call this kind of form? "Lao Jia"?
He referred to it as the 74 form (Chen Zhaopi choreography).
2. Who did he learn this from?
He didn't. I myself filmed some of these because he asked me to. He specifically told me that if people asked me how he learned it, to tell them he simply watched his relatives. And this is the answer that frustrated and confused many, and yet I believe it is the truth. From his perspective and even mine at this point this form is very easy to understand after learning our much more challenging CZK (83) approach. Learning, in this case is not required.
3. What does he think about it in terms of applications? He seems to have taught it too so I'm also curious why as for historical reasons I guess he doesn't think highly of it.
I do not think he cares very much about this issue to be honest. If you have a good understanding of our approach you will begin to see that although he demonstrates the 74 form here, the stance foundation, and body method are all derived from our line and his normal method. All he did was change the choreography, but people who do not train our line may think that is important. It is not important really. The important part is the gongfu within. In those days if people were to ask him the difference between the 74 and 83 forms he would say (publicly) "no difference, Dan bian is Dan bian, right?" Privately he would be a lot more nuanced; the big difference is the important structural and mechanical methods the either cultivate gongfu- or not.
At this time he was asked to send students to teach "Lao Jia" for some organization in Beijing so he trained some to teach it and sent them. Since he was working on that at the moment he decided to video and asked me to post some videos to, basically, confuse people. I think it worked.