I work commute and trail ride with my rovers with over 3500 miles between them in a year. It is usually 85-100 degrees for more than 6 months out of the year. I'm also +270lbs with about 25lbs of commuter gear (rack, backpack, accessories, spare battery). My understanding is the 500 watt limit on steep inclines is because of potential overheating and shortening motor life over time. I have to factor in my extra weight, high daily temps, and sometimes strong head winds of +15 mph and gust +20 mph. A strong steady headwind with a lot of gusts can feel just like a 10%-15% incline that suck battery power and strains the motor exactly the same way.
I have one spot during my work commute with fairly steep incline on the way home (my entire ride home is just one long incline up 550 feet over 6 miles). Probably 50-60% of regular pedal bike folks walk their bikes during this part. I have the newer controller programming with the watts are set for each PAS level (PAS 3: 375w, PAS 4: 550w). I can still pedal up those parts in PAS 3 or 4 depending on the mph I want to maintain between 8-17 mph. I'm also pretty tired, breathing hard, breaking a good sweat, and feel the lactic acid buildup in my legs when I'm trying to maintain the +17 mph up this section.
My goals is not to have sustained hub motor engagement above the 550w level for extended periods of time because of wind, heat, and/or inclines. Very easy to do with the newer "watts per PAS" controller programming compared when I had the old "mph per PAS" controller programming. I still use the throttle at full 750 watts power near the top of the hills for short runs if I start to slow down too much and just need a little boost. I've always set my PAS to 4 on this section with occasional bumps of full throttle as needed. Then back down to PAS 3 for the rest of the ride home.
The hub motor can provide enough assist if you adjust your gears and mph. You might have to check into changing the gearing to make your ebike into a better hill climber? My Radrover is not a hill climber with only 7 gears without the aid of motor assist.