The video in the previous post is a crash test at 30mph.
MN doesn't do well with multiple videos in one post, apologies for the double post.
In terms of tightness, another tough watch - this is how the crash test looks when the seat is installed correctly but the straps (and I think possibly the seatbelt) are simply too loose. (Red seat). It is really important to tighten the straps correctly, and ensure that the seat is firmly fixed into the car.
It looks to me like the seat in your picture is a generic/basic one, which is fine, these days these are actually not bad, but the main problem with them is that they tend to have fewer "automatic" or failsafe safety features. So for example, it is probably seatbelt fitted whereas I am guessing your Maxi Cosi might be isofix and maybe top tether as well? And the Maxi Cosi might even have something like a green indicator to show when the harness is tight enough (some of them don't). Seatbelt fitting is fine, but it is more prone to user error.
What you could do today to make your husband's car seat safer is go in and take the seat out of the car, sit your son in it, adjust the straps up so they are just sitting on top of his shoulders and the headrest is surrounding his head with his shoulders underneath it. Remove any twists in the harness, if you need you can fold the harness in half sort of diagonally and then pass the buckle over the fold if it's become twisted in the buckle.
Then if you have the instruction booklet, if there is an online video or even just the sticker on the side of the seat, double check that the seatbelt is going through the correct belt path in the correct order. For forward facing, you'll have red seatbelt guides, with blue being for rear facing (to be ignored for forward facing). Route the belt in through the guides and plug it into the buckle. Now pull the diagonal part of the belt, checking that the lap belt stays flat and in the proper routing (if it bunches up as you tighten, this is normally OK). Now ensure that the diagonal part of the belt is going through the correct places through the seat shell, and when it's all the way through, put one of your knees into the seat and kneel your weight into it while pulling even more slack out of the seatbelt. Now close any clips which are built into the seat or which are included with the seat.
If you are going to purchase another anti-escape clip, the most recommended ones are generally Besafe Belt Collector or Five Point Plus. But try having the straps at the right height first, because ideally it's better to use the seat without any add ons if you can get a safe fit that way.
I'll do a separate post to recommend seats if you wanted to replace it. But if you happen to be here and replying in real time, would you mind giving your son's height, weight and age (including months)? That will help to make a better recommendation for the seat - but I'll give them anyway if you don't reply.