OP, I’m not sure why you’re stalling, but it seems like 3x5 is not working for you, which is strange because most people can squelch themselves up to about 315 or more(I’ve seen up to 405x5!) before it stops working.
Are you saying you can complete 240x3x5, but fail to do 245x3x5?
If you’re not doing it already, try out the Starting Strength method for your Squat training, I have a hard time believing it is not working for you if that’s what you’re doing. (AKA do 3x5 and keep going up until you stall, then use the same weight that you stall on 3 sessions in a row, if you STILL stall, then reset down 20pounds or so and work back up, and if you STILL stall at the same weight 3 sessions when you get there and deload again and fail AGAIN 3x, then get off SS)
A program many people use with success in this number region of Squats is MadCows 5x5. My friend got up to a 585 squat using it, and it is extremely successful. Instead of squatting very heavy 3x a week, you ramp up to 1 set of 5 on Monday, do extremely light DE squats on Wednesday, and then ramp up to a heavy triple on Friday.
You can actually do this practice for squats without even having to call yourself being on Madcows, it’s a pretty simple principle, and one of the most valuable things a friend I have with a 700+ squat IRL told me:
Monday you can work up to a 3x5 with top weight ( for example 235x3x5 ), then Wednesday do 240x3x3, then Friday push for 240x3x5, etc. Rotating heavy 3x5 with 3x3 seems to help plateau bust when you are a newbie, and maybe that will work for you?
Also you may have some kind of glaring weakness you are not addressing.
If you have not read the program Starting Strength yet, you will notice you deadlift 1-2x a week, and eventually start doing “HYPEREXTENSIONS” very frequently. The hyperextensions may sound stupid, but they personally made my squat explode after my first plateau, and they really develop your hamstring/erector/glutes better than you think with a nice little squat crossover. Start implementing them if you’re not already, following the SS guidelines.
Hope this helps,you should not be stalling yet.