There are several different questions here that need to be answered. First of all, there are people in positions similar to yours that have gone on to become barristers. The sort of difficulties that you are describing are ones that are sets are now more alive to. However, it is really important that you appreciate that those candidates succeeded because they were able to show that they were excellent candidates notwithstanding their difficulties. You don't get pupillage because sets see no evidence that you're good enough but think they'll take a punt on you anyway. You still have to be able to demonstrate that you have the ability even with allowances being made for some weaker academic results or other shortcomings.
So no, you absolutely must not apply for pupillage just to see how it goes. It takes significant financial and time commitments to put yourself in a position where you can realistically obtain pupillage, and it's not a decision to be taken lightly. You must be confident that you can demonstrate the required skills. Otherwise you're going to waste a lot of time and money for nothing.