i think you are on your way there. though i believe there should be a more appropriate regimen to follow, maybe a mixture of jogging, cycling and some light weight liftings for weight trimming.

as for your weight lifting, nah that's nothing near to building muscles it is a good way to add on to your weight loss though(im assuming that's your main goal?).  if you want to add weight, you need heavier weights and a more appropriate sets. food intake is crucial too.

but if you really want to lose wright, then i suggest sticking to that first, because losing weight and adding muscle can be a bit contradictory at times. trim the fat, then look on to add mass to enhance the look

I would personally prefer a mixture. Less boring plus it helps work out different parts of muscles as well. If the gym u go have those rowing machines, u can try that out as well.

500 calories reduction a day is good actually, but I would prefer a combination of exercise + food maintenance. If u lose 500 calories a day but consume 3000 calories of food (assuming ur normal metabolism is 2000 calories) would mean u are gaining a nett 500 each day. Make sure u are aware of what u are eating as well.

Too much or not, your body will tell you ie. Dizziness, chest pain, shortness of breath etc. Don't over exert yourself. Other than that, if you can go on and have time to spend then I don't think there's any harm. The most important is to feel good after sweating and be healthy

1-1.5k calorie a day? when a human's average daily consumption is 2k? then how much u eating? 3k? lets put it in perspective. a bowl of rice is about 200 calories. that means u wanna burn off 7 bowls of rice worth of energy a day, just by exercise, on top of your normal daily metabolism. 

be sensible and think about the logic, dont just listen blindly. but if your instructor is talking about 1.5 KILOJOULES then that makes more sense because 1 cal = 4.2 joules. so 1.5kilojoules would mean about 350 calories. that coupled with reduction of food intake by about 200-300 calories, would mean a healthy way to reduce weight.

On another note, dont pay too much attention to the figures. no need to go "i need to hit at least 500 calories" or "i only lose 400 yesterday, today gotta lose 600 to make it up" etc. those are just figures to help you ESTIMATE your progress, not a definitive input. i dont believe those machines in gyms are accurate anyway. as long as you exercise, and know how much u are putting into your body, you are bound to lose weight, sooner or later.

if you feel pain and out of breathe, then you should stop. you shouldnt go full out when starting, that wont get u far before u get out of breathe. maintain a medium speed. the main thing is to maintain your heart rate between a certain level. too low and you might just as well walk, too high and it's not good for your body either.

it's a slow progressing thing. maybe jog for 15 minutes for the first few days, until you feel that after 15 minute jogging you dont feel out of breathe anymore. then you try to go for 20 minutes. over time your body will get used to it and as you get fitter, it will be easier and easier. stick to your own ability and rate, dont push yourself too hard.

The question on your workout can only be answered by yourself. I assume that by posting in here, you are working out with the goal of losing weight. After 3 weeks, do you see results towards your goal of weight loss? No weight loss but more toned in front of the mirror? If so, by all means keep it up.