Yep, 0.5g of EOD is enough. Keeping it lower is better because it keeps the estrogen levels at bay. Give this dose a try, monitor progress for 2 weeks, and go from there.
Everyone is different. 50mg/week might be normal for someone, while for others, it is low because they produce low testosterone levels. As a note, 50mg per week is about average. 100mg per week is generally the upper end.
Aromatase inbibitors might help with the crashes. Yes, HGH would absolutely help you maintain muscle. Discuss with your doctor about this, as it will drive up estrogen levels.