Odo was found by Dr Mora in infantile form in 2345, and DS9 starts in 2369. So if you consider Odo to be effectively 1 year old when found, he was only 25 at the beginning of DS9 (and basically a teenager when serving as its security chief under the Cardassians). Odo may act like he’s 50 (and his actor was 53 when DS9 started) but he’s actually much younger, and that explains a lot about his behaviour (his crushing on Kira, for example).
This is actually a pretty interesting line of thought. Rene Auberjonois was an amazing actor and his Odo was iconic, but would it have been better to have a younger actor? Or to have it stressed often (in much the same way that Dax’s characterisation often mentioned that she was 27 but she had two centuries’ worth of memories and experience) that Odo was in fact much younger than he pretended to be?
Because now we know this it seems very likely that Odo deliberately pretended to be older and more mature than he was (not unlike the First Doctor presenting as an old wise wizard, but later regenerations having got over that adolescent need to seem older). And yes, given that he was an enforcer for a brutal fascist regime for a decade when he was a teenager - it was his first job, poor lad - he was also much more traumatised and broken than he seemed. I think it’d have been nice to mention this during the flashback episodes.