I haven't been following this thread or topic as closely as you or others, but a recent BBC article does allude to the counter offensive exacting a very costly toll of Ukrainian lives. I assume based on this information the total number of Ukrainians perishing a week was extremely high at some recent point.
As recently as April, leaked estimates from the Pentagon put Ukrainian deaths at the much lower figure of 17,500. The alleged jump to more than 70,000 can be partly explained by the counter-offensive in the south. In its early days it was especially hard on Ukrainian infantry - "worse than Bakhmut" one brigade commander who is fighting there told me. The city in Donetsk fell to Russia in May in one of the bloodiest battles of the war so far.
Ukraine has now changed tactics there, but the beginning of the push to breach Russia's occupation defences in June was costly, for young newly trained soldiers in particular. They were dying "by the dozens" every day, one senior sergeant fighting around the Donetsk village of Velyka Novosilka told me in June.
The article also explains in part why the questions you asked are proving so difficult to answer at the moment. I don't think we'll have any exact information for years to come.
Ukrainian Deputy Defence Minister Hanna Maliar earlier released a statement warning that those who release casualty numbers would be liable to criminal prosecution.
"Why is this data secret?" she asked rhetorically. "Because during the active phase of the war, the enemy uses the number of dead and wounded to calculate our likely further actions… If the enemy has this information, they will begin to understand some of our next steps."