I have been using those for the last 18 months or so and have reused them a few times without any problems. Just turn them inside out to wash them taking care to get right into the corners. It is a shame they do not make them with rounded corners to make it simpler.
I prefer my meat rare to medium at around 53C so other than one time when I did a steak for a cousin who wanted hers well done and I set it at 65C while I cooked hers and then dropped the temperature to do mine and my nieces, I have never had anything at a higher temperature in those bags but I think i saw that they were sold as being safe to 100C
I had exactly the same pump but the kit I got only came with the two largest sized bags and when it arrived it only had the single clip and not the two that it was supposed to have. I didn’t bother at the time but I will be annoyed if I lose it or it somehow breaks as it makes it so easy to seal the bags using it. I always run it right across from one end past the other then place it on that end and run it across again to the first end and then it works really well.
I have since bought an electric vacuum and sealer and rolls of bags but until I use up my stack of existing bags or the pump fails I will carry on using it
The only advantage I can see of using the electric vacuum sealer over those bags would be that they say to keep the valve part above the water line whereas with the fully sealed bags you can submerge all of the bag, so I always clip my bag to the side of the water bath with a clothes peg so that the valve part is a little above the water line.