My opinion, and it is only that, is that I wouldn't bother with filters to start with. The Moon is really bright for sure, but if you're observing the Moon then you're not really worried about night vision (you could do it just as well from home if you have a clear shot) so just peep at it and let your eyes adjust. You will get more contrast without the filter.
Light pollution filter...unless it's really bright where you observe from (you can read a book without a torch) then don't rush into getting one as all they do is cut light throughput.
Same goes for a nebula filter (the one you linked to is for an SCT so definitely don't get that as it won't fit!)...for a small aperture you'd be better off with a wide band UHC filter as it will let more light through, but the downside is that the reduction in unwanted wavelengths and consequent enhancement of those you want is much more subtle than in a larger scope with a narrower band UHC type filter. That's my experience anyhow.
A chair is a really good suggestion, it's much easier to observe for lengths of time when you're comfortable! I can observe Jupiter for hours at a time and being seated and positioned well is really important.
Barlow...make sure it's a really small and light one for it to work well with the focuser assembly on the Heritage. Baader do a really nice little one that really seems to introduce nothing optically besides magnification (but it isn't cheap) but there are plenty of others to choose from.
The important thing is just to get out there and enjoy your scope
there are lots of satisfying targets easily in the reach of your scope and there will be plenty more to come as we approach winter
