One last question, If i wanted to use a different relay with a higher resistance coil, the load on the transistor should go down, right?
That is correct. If the relay can handle the power demanded, then it is perhaps a good idea. The only other consideration is that automotive relays are made for harsh conditions, vibration, and high temperatures that another relay may not be.
I am currently still bench testing the board, but i just left it on 100% for about over 60sec and the transistor didn't get much above room temp.
When it's 100% turned on, the transistor is saturated and is dissipating very little power. The dissipation increases as the capacitor discharges and the reduced base current means a higher voltage across the transistor.
The worst case is probably if the relay only just stays pulled in in the interval between flashes.
Ok, After testing i think i may swap the 10K pot for a simple 10K resistor. would is hold a bit longer if I replaced the 470Ohm that is in series with the pot with a larger one? I think it hold's enough as is, but I wouldn't mind it holding a tad longer.
Increasing the resistor will increase the delay up to the point at which you can't supply enough base current and the relay either doesn't pull in, or drops out soon afterward.
If 10k + 470 ohms is not enough, I would consider a slightly larger capacitor (what are you using now?)
Once you have determined a suitable delay, measure the resistance of the pot and replace it with an appropriate resistor.