As you have found out by talking to Toro, there are NO Answers to your questions that will ease your mind. We have not had a lot of problems with these starters. You may have just gotten one that failed.
1. You cannot get parts for this starter because they do not make or offer any replacement parts for them. The only offer the starter gear assembly or a complete starter assembly. This is going to be the norm for most equipment manufacturers for years to come.
2. We cannot give you information that we do not have. I have been a very large TORO dealer for almost 30 years and would give you the help you want if it were available.
3. There is no way to assure you that the next starter will do better than the first one, but if I were guessing I would probably guess that you wouldn't have the same problem with two starters in a row. We just do not have many problems with them.
4. My job here at JA is to give the customer the best possible answer to a question based on my vast knowledge and experience. I cannot guarantee that the answer that I give is the answer that the customer wants to hear. In fact a large number of the answers given here at this site are just the opposite of what the customer wants to hear. Just because the answer you get is not the result that you want does not mean that my answer is wrong. It's just like asking a parent something and sometimes they have to say NO. The answer cannot always be YES.
I have spent a great deal of time trying to help you with this question and feel that I have done my job well, it just isn't the result that you wanted. That happens.
Your answer, in a nutshell is: if you want this unit to operate properly with the electric start, yo will have to buy a new starter....or find a used starter at a dealership that has junked one of these snowthrowers and kept the engine or starter....or...you can keep checking E-bay for one and buy it there. If it lasts a long time....great....if not, then that is the risk that you will have to take. There is no other answer....no matter how many times you rephrase the question ,....or ask for more information......
I really hope that you can understand this. I am trying to help. and have been very patient trying to help.
There is no other answer...
So I have done my job well and provided all of the available information.
It is now up to you as to what you do.