You'll generally burn about ~2k cals per day just being alive. An intense workout for an hour can burn maybe 500 on top of this. I think your math might be off somewhere if you walked a lot and figured that you spent a whole 1k.
No, not even close. I would expect 4-5 hours of walking to burn significantly more than that.
On top of this, it doesn't "stack" well because of the low heart rate usage, meaning it logarithmically increases calorie costs (our bodies essentially amortize it), whereas lifting and carrying a heavy object for 20 seconds exponentially increases it.
Cardio is continuous work while lifting is work done a few seconds at a time.
Walking in particular is still moving your body horizontally through space. That horizontal displacement is the biggest determinant of energy cost for any given body, all things being equal.
Running only burns slightly more per unit distance because there's slightly more vertical displacement as you're literally leaving the ground between steps.
For a fat dude, it's about 150 calories / hr for sitting vs 350 for walking.
Source: google. Use appropriate doses of salt.
William Goodge smashes record after running across Australia in 35 days
British athlete four days quicker than previous record holder who completed 3,800km feat in 39 days
Spurred on by his mother’s battle with cancer, and with his father by his side, William Goodge crossed the finish line in Sydney just after 4pm on Monday.
It brought an end to 35 days of pounding the pavement, striding the equivalent of two-and-a-half marathons a day.
> Shannon-Leigh Litt has run 500 ultra marathons in 500 Days
https://www.stuff.co.nz/sport/360690060/northlander-runs-her...
Out of reach for most of us though.
Or incorporate more strength training that increases type IIb adaptations and greater BMR.