I expected a few replies to you but as none have appeared (yet) you may have to make do with my thoughts. ... Apologies in advance. I have fiddled / meddled and generally cleaned up a fair few Standards in the past. They are very easy to work on but you do need to watch out for a strong mainspring at times. This is not an issue per se if you are careful on stripping the rifle but can give difficulty on reassembly unless you have a means of holding the action or end block captive while you compress the mainspring and start the end block threads going. Have you found the strip instructions on the Idiots Guide? Have a look if not, thread 112.
Regarding the tap ... If there is wear on the tap or indeed the hole in the action that the tap rotates in there is not a lot you can do without attracting expense. You may find a new tap from one of the spares suppliers (I have not checked) and it might well fix your problems but be prepared to maybe adjust the fit as I think most are supplied a tad oversize. And be careful to get the pellet bay in the tap exactly in line with the bore. Get it wrong and the pellet will 'clip' as it passes from tap to bore, losing power. In the past I have tried all sorts of remedies to cure leaky taps on all sorts of rifles and have not yet found an easy, cheap, reliable way of doing it. For an Airsporter I once resorted to making a new tap from the shank of a steel bolt. It worked but took a long time (my first attempt failed as I got the alignment out by a fraction of a mm). I believe it is possible to get a tap plated but do not know the cost.
You say the power is currently 8ft lbs. That is not too bad. Yes, I have heard of the Standard going up to 11 or above but I have never shot one at that level. I wonder if it becomes harsh? If the mainspring is very old then it could be weak and a slight increase over 8 may come from a new spring .. if I remember correctly you can fit an Airsporter spring.
Regarding the original Wasps... not very common. They do appear on 'the site' now and then and also at various auction houses on-line etc. But I have never bothered to search for them as I find most .22 pellets are OK in the Standard, although there are differences in power between them. I think Knibbs do a 5.6mm version of Marksman pellets if you want to give them a go. Do I remember the new Wasps being available in 5.6 and 5.5mm?
Wishing you luck ..
Cheers, Phil