Also if you've 40 hours to go, I'd suggest sending an individual DM/tweet to each of your followers who haven't backed you...reminding them the campaign will end.
I've seen the style of your tweets already, so you've got this covered but to everyone else:
You need an "action" point of telling your followers what you want them to do.
For example, if you've 40 hours to go say something like:
#40hours to GO! XX (campaign name) is ending soon. We'd appreciate your help and please RT us *link*
Neda811 wrote:Mentally be ready for cancellation. People change their mind and cancel their pledge.
The reminder letter Kickstarter sends 48 hours before ending the campaign can be the last momentum for your campaign.
We have 40 hours to go and still hopeful to unlock a stretch goal. Never give up!