messed up replacing the rubber gasket on the TPM

[petepro]

I had a slow leak in the rear wheel so rather than chase the problem I replaced the rear tire. ( it was due anyway)

While I had the tire off I swapped the little rubber washer/gasket on the valve stem. 

At this point I thought I was doing great until I grabbed a standard instead of metric hex and managed to round off the TPM.
The valve was seated and it seemed tight so I quickly and anxiously mounted the rear tire.   Then I realized I put it on
backwards and had to flip it.  Then filled it and now I think I still have a slow leak.   No bubbles near the valve stem.

So two questions. 
1) Do you think the TPM hex hole could be slotted with a dremel for either removal or just tightening it.

2)  how the heck can I track a slow leak?  Keep in mind I live in an apartment and I'd have to wait for my wife to leave if I need to put it in a dunk tank. (aka Bathroom Tub)

[VirginiaJim]

If you have the standard TPMS module in the tire, dunking it in water would not be a good idea as it may short it out.  Spray windex or other soapy solution around the the valve stem to check for leaks.  You can also spray the entire tire with it as well and watch for bubbling.  Take the valve stem cap off and spray it in there as well.

[Flat-spot]

If you do have a slow leak, (tire is holding air pressure) go ahead and dunk it. Water will not get anywhere near the circuitry. Air pressure won't let it.
There are a number of things you can try for the stripped allen hole.  I have had success with hammering a slightly bigger Torx socket into the hole and then leaning into it with a cordless impact driver.
I've changed batteries once and tires 14 times in 7 years and never had a problem with that washer.

[just gone]

  I have had success with hammering a slightly bigger Torx socket into the hole...

What he ↑ said...but before you try that, get the right sized metric hex/allen wrench and grind or sand the end perfectly flat so it has 6 sharp edges on the tip and force it deep into the stripped hole and try that first. (a tip proudly stolen from MOB)

Spray windex or other soapy solution around the the valve stem to check for leaks.  You can also spray the entire tire with it as well and watch for bubbling.  Take the valve stem cap off and spray it in there as well.

What he ↑ said...but a slow leak doesn't always show when you are staring at it, walk away for 3-5 minutes or so and when you get back you should see a small acorn sized pile of bubbles on the tire somewhere. You did clean the insides of the rims between tires right? My slow leaks are always on the rims.

[petepro]

1) Do you think the TPM hex hole could be slotted with a dremel for either removal or just tightening it.
2)  how the heck can I track a slow leak?  Keep in mind I live in an apartment and I'd have to wait for my wife to leave if I need to put it in a dunk tank. (aka Bathroom Tub)

Thanks for the suggestions.   Once again this forum rocks.