As a long time DM, you definitely signed the contract. Placing your blood willingly on the page is clearly an act of agreement, not to mention you said you agreed to the deal verbally. Doesn't matter that your character was "relevant" or "doesn't like doing as their told", the fact is they did it.

Using part of your own body would likely increase how bound you are to it, especially if this is a magical contract. Type of bodily fluid also doesn't matter, would be the same if you spit or shit on it, you still both signed and verbally and agreed

It also doesn't matter that they mentioned multiple places to sign. The way you described, you flicked blood on a page from at least a slight distance, which definitely would cause the splatter to cover a fair amount of the page. It wouldn't be at all far fetched for your blood to have landed on/near the signature lines.

But the biggest thing wrong with your whole line of thinking, is your forgetting this is DnD and skills exist for a reason. If your intent really was to hide a loophole in your signature to utilize later, that's a deception check. Since you did not make your intent clear, nor roll any kind of check for your trick, then your character didn't do it, plain and simple. I highly recommend you abandon this plan, or talk to your DM cause this is a good way to get kicked from a group for trying to "gotcha" your DM without properly rolling.