Hi,
I just wanted to notify you that I did train another Italian model some time ago, which you can find here: https://gitlab.com/Jaco-Assistant/deepspeech-polyglot
I did use about the same amount of training data like you, but got much better accuracy results (0.248 vs 0.399 WER on CV-test), so you might be able to find some ideas for hyperparameter optimization there.
PS: It would be great if you can share a link to your model in the pretrained models collection thread: https://discourse.mozilla.org/t/links-to-pretrained-models/62688