The tabs are stuck on with the same glue that is holding the battery down. It is fairly strong but will come off with some patience and consistent progress.

Despite the photo, I do NOT suggest using the tweezers for this but the black plastic spudger that comes with the kit. I say this after having the tweezers lose grip and slide across the bottom black ribbon attached to the case. If you must use the tweezers because of the strength of the glue, use a downward force into the case bottom, not an outward force. That way, you will not have the same happen to you…

Here is hoping the slight scratch did not damage anything vital…

Like others have said, THIS STEP IS THE MOST DANGEROUS!!! You must be extremely gentle (no real force should be necessary to separate the screen from the glue) with the screen and take your time. (IMO if it takes you less than 30 mins to get the screen loose, your going too hard at it). Two suggestions from my successful battery replacement that I can give, use alcohol instead of heat (seems to work better with this phone) and start with a much thinner plastic tool that is also flexible (I used a metro card from the NYC MTA). This will allow you to get at the tiny gap without using any significant force and then get some alcohol into the gap by dripping it down the thin plastic tool. Honestly, IFIXIT should make a small thin rectangular card to use for this with lines around it for measurements…