I really liked this, and historical fiction isn't something that I read much of, so well done for keeping me immersed and interested!
I haven't got anything to add really to the excellent feedback that others have given you above, and I'd concur with pretty much everything that's been said already.
You're a terrific writer, and your prose is a pleasure to read. I think, though, that you might suffer a bit from the same affliction I do - a visual imagination, which creates a tendency to try and get every single tiny little detail down onto the page so that the reader sees exactly what you see in your imagination! 😂 Which inevitably leads to a degree of over-writing!
It's hard to step back and allow the reader space to create their own version of what you're writing... with just enough detail for them to get the essence of the scene but with enough left out to allow them to populate it from their own imagination and experience.
I deal with my own purple prose by doing a quick 'pre-edit' immediately after I've come to the end of a passage or a chapter (or even a paragraph). Just to glance through it and strip away the repetitions, unecessary adverbs, redundant dialogue tags, and split up some of the longer sentences with multiple clauses! I don't always succeed, as the feedback I've had from others here will testify! But it's a useful exercise nonetheless, I find.
Tightened up and simplified just a tiny bit (without diluting or changing your overall tone, which is wonderful) this will be a terrific read. The historical aspects seemed to me utterly believable, the characters are vivid and compelling, there's a real sense of place and time, and I though Marcus was a terrific protagonist and I wanted to know more about him, and his situation.
A thoroughly enjoyable read!