There seems to be a short to ground in the wiring somewhere.
The fuel pump is shorting out and that is why the ecm fuse is blowing .Disconnect the the fuel pump and try it again,if the fuse blow's again then it is not the fuel pump.
Check for recalls first then I would estimate either an overload on the circuit, bad wiring harness between particular fuse and the component it powers, or a loose wire.
The best option for this is to go to the owner's manuel for your Blazer. If the fuse number is not listed there, contact your closest Auto Parts store.
A short.
NO.. It will not.
It being an American vehicle
Check the turn signal relay. The four way flasher and the turn signals each have their own relay. It has a fuse for the turn signal
Yes that could be the cause. If you keep blowing a fuse, either you have a short, loose connection, too small a fuse, or the circuit is overloaded.
You likely have a frayed wire to the stop light.
Really....? Find the fuse in the fuse box (either in the interior fuse box or the one under the hood), pull the fuse out, see that it is blown, replace it WITH the SAME size fuse. If it keeps blowing there is a wiring issue.
Check or replace the socket
Because the turn signals are a completely separate curcuit from the emergency 4 way lights. The turn signal wiring has a short that causes the fuse to blow out. In order to find that short, you need a technician that specialises in electrical wiring repairs, because you could spend days trying to find it and fail. It will cost some money but less than the value of the truck, or a traffic ticket for "no signals."