The hand guard pin is a bugger. Often it's been mushroomed after it was installed and there's no good way to get it out. It's just a pin though and I wouldn't hesitate to cut or drill that mushroomed area to keep from having to hammer the crap out of it and possibly damaging something else. Others have replaced that pin with a simple nail or tack, also mushroomed over after installation.
The Intrafuse hand guard probably has four or six little tabs on the bottom, these are also for fitting reasons. Once you get the hand guard on, it may be too tall to allow you to latch down the gas tube. If that's the case, just file off a bit of the tabs until the latch closes properly. Just a bit at a time. These tabs will also keep the hand guard from wobbling if you decide to take a chance and mount an optic on it. If you take off too much you can always shim the hand guard to take up the slop.
You also have the option of buying a complete US made gas tube. These typically have a steel vented hand guard, this is also a compliance part. It's an added expense but it does keep the original gas tube/hand guard in good condition. But since yours is already sported, this could be a pointless option.