Well.... Let my try to be helpful, while carefully trying to not seem condescending (which I certainly do not intend).
There's a saying that you can have a thousand hours, or an hour a thousand times. You'll quickly figure out how that applies to a hundred hours or less too.
After 34 years, and many thousands of hours of flying, I took a PPL ground school again this past spring. I was stunned to be reminded how much is not taught in ground school, and by extension, in most flight training. It's just not on the required curriculum, and students are probably already grimmacing about the amount of flying to qualify for an examination as it is - they hardly want more! That does not mean it would not be very valuable. It just will not fit into the first 100 hours, no matter how you push on it!
Those more experienced pilots (who operate grass strips, rent out aircraft, and choose who can be eligible for shares) generally know this. They are looking back on their experience, and figuring out where their comfort level starts and stops for less experienced pilots. 100 hours is really on the low side.
When I had 1000 hours, I though I knew it all, and was probably quite dangerous. Many thousands of hours later, I think I will one day be a good pilot, if I stick with it, and apply myself. In the mean time, I keep my mind open for more experience. All fixed wing insurance companies regard me as insurable (in my realm), and many people seek me out for checkouts, and other flying. I still have lots to learn...
So where's the advice, which might help you? The collective experience of the instructors you fly with has it's own "glass ceiling" which will be very difficult for you to determine. I'm not saying it's low, but it could be, and you cannot tell. If one of them has grey hair, you've got a better chance. There will come a point where continuing to fly with them, at best gives you more total flying time, during which, hopefully, you will statisically have more experiences. I know how you feel more than you think. After earning my helicopter license two and a half years ago (which involved lots of solo flying as a student) I have not flown any of my subsequest 60 hours as a PPLH solo. Everone likes my flying, but no one's insurance will cover me! So I fly with other pilots, and continue to learn immense amounts.
You are better to relax, lean back, and submit to the experience (as opposed to total flying time) expectations of those who control the use of aircraft and facilities. Align youself as best you can with these people, and make it very clear that you know that with a PPL, you are at the very beginning of your flying education. As you "hang around", and do some flying within their "view", they may come to relax a little. If you're sharp, pick up lots, and if they can see this, the time requirements may fade, in favour of your obvious broad experience. In reality, by the time you reach the point of demonstrating this level of skill, you probably will have passed 100 hours!
Trust me, years form now, when you have thousands of hours, you'll look back, and think, yeah, now I understand....
Unlikely I would let a 100 pilot fly my C 150 out of my grass strip, unless that pilot had demonstrated super skills to me over a number of hours of flying together. But that's just me... Think of it from the point of view of the aircraft or airstrip provider, any minor ding is going to cost them money, and loss of use of the aircraft. Was the 10% profit on those couple of hours of rental to you worth that cost? Probably not. The risk mitigation says just don't put the aircraft in that risk. It's just really difficult to quantify the point where the risk drops to being reasonable. An hour a hundred times is a worry. A hundred different hours is a very good start. Show 'em what you've got!
Sorry to not sound more positive. If you owned the aircraft or runway, you would probably not be offering it to inexperienced pilots for all the same reasons. Bear with us, and be patient, you'll get there...