Clueless about keeping weight low

So, a little resume.. I am 19 , 6'2" 168, just lost 70 lb, my calorie intake is around 1500...

Now i want to build a little muscle (just to keep it nice actually not to gain muscle mass) and i was wondering if anybody knows:

1. Will i get fat if I increase my calorie intake to 2000, because my calorie intake was low and i'm afraid that my body will not metabolize all these calories.

2. How to keep my testosterone level high?

I usually spend about an hour in a gym everyday, with light to moderate activity. The thing is that summer is over and college gives me a lot pressure so i also want to decrease my gym hours to 3-4 per week...

Please if anyone has smart ideas please help, i would really appreciate that

You should run your stats through the CC calculator setting your activity level to 'moderate'.  Assuming you're male (the testosterone reference) I calculate you need between 2700 and 3300 cals a day to maintain your current weight.  The higher figure when you exercise, the lower figure the rest of the time.   (If you're female those numbers become 2200 - 2700.)  You should expect to regain a little short-term but it should only be a temporary effect.  If you're male, you've been crash-dieting unfortunately, so there may be a larger increase initially.  Be prepared for that but don't panic.

To keep testosterone levels high follow a well-balanced diet .... 50-60% carbohydrate, 20-25% protein, 25-30% fats..... and get a good range of different foods including leafy greens, red meats, eggs and fats.  Animal proteins and foods with a good zinc content are especially recommended.  If you want to build muscle and increase testosterone levels make sure you eat enough food in total in total i.e. don't skimp on the calories.  

hmm now i eat 1800 calories but feel too full after my meals, so i asume that my metabolism has decreased? Does anyone one how to increase it again? Because i already eat 5-6 small meals per day, balanced meals, workout ant all such small stuff... I just don't want to get any of my weight back that i lost ... ;(

You increase your metabolism in part by feeding your body more food.   It's very easy to do so by either increasing portion-sizes slightly, adding more oils to your foods or adding in a few low-bulk, high energy snacks such as nuts or dried fruit until you get to the right level.    Avoid eating too many high-bulk, low-calorie foods like vegetables because they fill your stomach up well before you get the right amount of calories.

The risks attached to chronic undereating such as nutritional deficiencies are well-documented.    Too little food - even if it's well balanced - is not a healthy diet.  And of course, if you want build muscle, you can't if you don't take in enough energy.   If you continue to undereat you'll keep losing weight, albeit slowly.

If your fear of gaining a few lbs is negatively affecting your life & seriously standing in the way of you eating normally and healthily then that is a concern.  It's unfortunately quite common for something to start as a health-kick but then to spill over into something unhealthy and obsessive.  If you think you're in that area then do talk to someone.  If not, then do your body a huge favour and start upping the calories.