I have the rule that if I can’t get the weight up myself then it’s too heavy for me.
If you can do 80x5, then you should be able to get the weight up yourself without a spot. You know the technique right? Is it getting the weight to the chest that is the problem? Or is it pushing it out from the chest on the first rep? If it’s the latter, then you may be starting with your elbows too far out. Or maybe a bit of both. If You can’t get the weight up high enough with your knees, it will make the first rep harder.
Just for completeness, I’ll post the technique I use to set myself up on the incline bp. I think it’s the standard way, but it’s worth repeating.
While standing with the 2 db along the sides with the incline bench behind me, I put the dbs on my thighs and sit down. Both dbs should be on your things when you are seated. Once you are in the correct position, clean each db to your chest with the assist of the corresponding leg by lifting your knee. You do this one side at the time. You should be pretty close to the bottom position of your presses.
You probably don’t need a spot at all unless you are working beyond failure. I noticed that spots on inclines usually do more harm than good. A lot of times people push the elbows too fast or unevenly.
Now if you have a ROM problem that makes the bottom position of the db press difficult, then I would suggest you skip the incline db and switch to the barbell which is also easier for people to spot.