I’m going to preface this by stating that I am not an electrical engineer… Modifying electronic devices & removing enclosures to expose live conductors is dangerous. Know the risks! I wouldn’t plug this in without an rcd or similar device being between the mm & your source of mains electricity.
The main issue there will be your ac terminals. There are iec standards which tell you the correct clearance required, based on a whole range of parameters. I’m not qualified to give you an actual distance, but if it was me then I’d be looking to do at least the following:
Use some kind of ‘stand off’ to physically stop the bottom of your board from touching the metal case. Think of the type of standoff you would use on a motherboard for example. Thesr can be fitted to the corners of your board.
Use a thicker, solid insulation… That sheeting you’ve shown would be easily punctured by a sharp bit of solder at the bottom of your board. I’d use a solid piece of plastic underneath it as well (got any old plastic lids from a takeaway container?)
Finally as you’ve cracked open the case of your monitor consider if there is a chance that you now have metallic elements which could (under fault conditions) cause a shock if touched. Is the chassis earthed?