Hi Mark,
Don't be too discouraged. A lot of the things you said are indications that:
1. You care.
2. You have very good fundamental musical listening skills.
and
3. You try to do the best job you can.
In other words, the fact that you noticed these problems are an indication that you were listening and paying more care and attention to the music then perhaps the other people who were on the gig were (you mentioned others did not seem to notice the issues, not sure if that was the audience, your other band members or both). It is actually funny how 4 or 5 different musicians on the same stage can have a completely different take on how well a gig goes. I have done gigs that I thought were pretty bad while the other musicians loved it and vice versa. Even if the problems all come from one musician (which is not likely) the other musicians should have noticed the problems no matter how well they were playing. If they do not notice then they probably are not lisenting enough.
Anyways, the first step to getting better is being open to noticing problems and you have shown that you are open to that. You cannot solve a problem if you are not aware of it, so it is actually a good thing in a way when you notice things that are not going well on a gig. Even if noticing this stuff makes the gig less enjoyable, at least you will be helping yourself to improve as a musician and helping the music to improve over time and even immediately while on stage during the gig. People who do not pay attention to these things do not tend to improve much over time and neither does the music.
I am a full time drummer and I have been doing about 100 gigs a year for the last 4 years or so. I have come to realize that how well you play on any particular gig is based approximately 50% on your current skill level and 50% on the situation (please excuse these obviously estimated numbers). So when you have a bad gig, try to not to make big assumptions about your skill level, because bad gigs sometimes do not actually have as much to do with your skill level as you might think.
The skill level part is self explanatory but the situation part is made up of lots of elements including:
1. The skill level of the other musicians you are playing with.
2. The quality of the sound system, sound check and the acoustics of the room (room acoustics can make 1 drum set sound and even feel completely different from one room to another)
3. Drums are usually a supportive instrument so it can be difficult to play well when the people you are supporting do not know their own material very well. So, how well the other musicians know their material can affect the situation as well.
I have checked out recordings of myself from years ago and thought "Wow, I have improved so much since then". But I have also checked out recordings of myself from years ago and thought "Wow, my playing on this old recording is actually better in some ways then my playing on some gigs I did last week haha".
So, it just goes to show how much the "situation" can affect your playing. Sometimes you play very close to the upper range of your skill level and other times you play well below the upper range of your skill level to the point where you are actually playing at a level you were at years ago. When I say upper skill level, I do not mean in terms of how complexly you are playing. I just mean in terms of how well you support the music through the use of all of your knowledge and skills. I like to think that the situation effects your playing less and less as you get better and get more experience (and I think this has been true in my case) but I still think that the "situation" will always have a significant affect on someones playing on any particular gig no matter how good they get. I guess the basement level and ceiling level of any musicians playing is set by their current skill level. Both the basement and ceiling levels will both get higher as they improve. However, the level they play at within that range (on any particular gig) will largely be decided by the various aspects of the situation.
I do about 110 gigs a year and to be honest the majority of them are not amazing. We do the gig and it is usually enough that people enjoy the music or dance etc.. but it just seems that the realities of full time local level gigging are just not conducive to the idea of playing really great "polished” gigs every night. However, I can say that when you do the odd really great gig it feels pretty good and playing music in any way is a great experience anyways. At the very least you end up with a number of great "bad gig" stories (that are hopefully funny) to tell and these stories are what pass the time at rehearsals
Anyways, I think if you stick to it, the gigs will probably get better.
Hope that helps Mark and happy gigging!