Cross-Bike for my size / weight I'm 183 cm / 100 kg (220 lbs) and was thinking of buying a bike. I was looking at the following models:

Trek Bike 7.4FX (http://www.trekbikes.com/us/en/bikes/city/fitness/fx/7_4_fx/)

and

Giant Escape RX3 (http://giant.co.jp/giant12/bike_datail.php?p_id=00000044&amp;action=outline)


Are these two models strong enough to hold me?
I am planning to ride the bike on roads only, but maybe a dirt road or a road with cracks or even holes once in a while. Are the tires strong enough?
The tires are 700-32C. Can I say the wider the tire the stronger?
I am not sure about the absolute weight limit. Can you find it? Is it 125 kg / 275 lbs? (Maybe I want to put some stuff on it. That's why I'm asking.)
If I need a weight limit to up to 136 kg / 300 lbs, do I need to consider a mountain bike?


Thanks in advance ...

B
A mountain bike is not going to be inherently stronger. 
If anything a larger frame triangle is stronger.
On a mountain bike you have a long seat post that is a point of failure.  

I don't recall seeing weight limits posted for bikes.

Consider a touring bike as they are designed to handle a load. 
Or an expedition bike. 
I would go with a high quality steel or titanium bike.  

Some wheels will post weight like Stans posts weight for some of the wheels. 

And larger tires do take more weight.  You always see larger tires on touring bikes.  Weight = contact area X psi.  A larger tire generates a larger contact area with less deformation.  A larger tire protects the rims.  The wheel still must bear the weight but the rim is cushioned from that ding associated with pinch flat.       

With light use I suspect those bikes would be OK.

From Trek up to 300 should be OK.
Is there a weight limit for your bikes

If you are targeting 300 lbs then consider some more expensive bikes. Like a Salsa Vaya or even more $ a Moots Routt 45.