The hub score required to make the links do-follow is 40, not 75. 75 is the author score required. So, you need to increase your author score.
Being active in forums help a lot. Answering more questions and comments also help.
The problem I have found in your hubs is the use of same domain in every hub - thertasore. This might a potential link spamming in the eyes of HubPages and this might be the reason why your author score is low.
If you write a few hubs without mentioning the domain name, then it might help. I would suggest you to interlink your hubs and put the external domain link in only one of the hubs, not in all.