I am stuck at 5x75 kg bench press.

I bench press once a week for 4 sets and overhead press once a week for 4 sets.

I could increase the frequency by training 3 times a week instead of 2, or I could increase the number of sets to 5 or 6. I am sure either of these approaches would work.
However I do not want to do this since I find going to the gym boring. 

Instead I want to progress, but slower. 

Earlier I did linear progression: 4 set x 5 reps. But when I came to 5x60 kg adding 2.5 kg each week was a ca. 4 % increase in 1RM and I could not do it.

I then switched to double progression. So instead of doing 5x62.5 kg the next week I did:
6x60 kg: ca. 3 % increase in 1RM. Once I hit 7 reps on the top set I added 5 kg and worked my way up to 7 reps again.  

Now even this is too fast progress. I find it demotivating not being able to add 1 rep each week.

One option could be to switch to something like 5/3/1. Here I could progress as slow as 2.5 kg every 4th week: ca. 1 % increase in 1 RM per week. However I do not like the idea of a preplanned work plan based on percentages. I like looking at my log book each workout and deciding on the spot what to do.

I have come up with an idea that I wonder if anyone here has some experience with or thoughts on?

I alternate volume and intensity weeks. On volume weeks the aim is to increase the total number of kgs lifted.
On intensity weeks I work up to a heavy top set. My goal is to increase the top set by one rep. I start at maybe 3 reps and once I hit maybe 5 reps I add 5 kg and work my way up again. This way I could progress at the slower rate of 3 % every second week.

This way I could still decide from my log book what to do each workout, only this time I would have to look at not the last workout, but the one before that.