I am only at 80lbs for OHP so it is getting harder but I have not experianced the first push struggle you are describing. If you can get 5x5 with good form, tight glutes, tight abs, then keep adding. When you stall or fail, next time you do the lift, don't add, after 3 stall/fails of getting 5x5 deload 10% and continue like before you stall/failed.

As for eating at a deficit while doing SL5x5, I have read mixed opinions. The majority is that you "can't" gain more then "newb" strength while eating at a deficit. There is also the idea that you can not lose weight unless you have a calorie deficit. I could not tell you if this is fact or not. I know plenty of people that do IF (intermittent fasting) gain stregnth and drop "FAT" some drop lbs off the scale but most measure thier success by inches and body fat %.

I started MFP and SL5x5 because I wanted to decrease my BF%, but after learning more about heavy lifting I decided to change my goal to gain more strength and get 12-24 weeks of SL5x5 done. Revisit my goals and then decide to cut and decrease caloiries. When I first stated SL5x5 I was eating at a deficit, had my calories goal set at 1920 ( I am 197lbs 5'11") I did not eat back calories burned on work out days. I think it was around week 3 that I started feeling like crap, tired and out of energy. I read a little more, talked to some of the guys on the strong lifts inner circle and thats when I changed my calories to 2500.

Listen to your body! Ask as many questions as you need to. Do research to back up the stuff you find on the forums. Hit me up any time you are wondering about something. I am always around.