Music Man Amps

Hey guys, I am so glad I found this board. I think you will see more people like me in the future. These amps are starting to develop a reputation with the Indie scene as being an incredible pedal platform. I lucked into a 212HD 130. It is a model with the 12ax7 preamp. The serial is 0000390 -- which seems early. I could certainly be wrong. I LOVE THIS AMP. Let me start there. I am almost certainly going to make this into my main amp over time, but in the meantime I have some "gremlins" to work out. I am certain there are answers to all these questions in this forum but I am going to ask them here anyway because I am hopeful some kind person who knows most of these answers will just rattle them off without me having to dig for a few hours.

So, here we go:
1. The second input on the channels-- its actually sort of an effects loop- using pin-rod- sleeve? I have a Crate Vintage Club that uses the same idea if so. BTW-- those amps are maybe, nearly as under-rated as these.

2. The manual says to keep the master volume at 10, and always use the high switch setting. It also says to not use the second input on either channel without using the first input. I have seen people online saying they to the opposite on some these things. What is going on with that?

3. My reverb channel input, i have to leave the cable unplugged about an 1/8 of an inch to get sound. Is that a bent jack? Where should I find a replacement?

4. When I power it off, I get an odd crackling sound. its sort of like cooling glass-- I assume that is the tubes, but I have never heard this before in any other tube amps to the degree I hear it here.

5. The 12ax7- I would like to update to a more robust tube for safety of my output trans. The links that are referenced in older posts seem to not work/ are not able to be found. Where can I get an upgrade like this? Is it as big a problem as people make it out to be?

6. My tremelo is dead. The rest of the channel is fine. I will at some point check the internal bias-ing pot to see if it got out of adjustment,, but any other easy ideas? I am thinking I can live without the tremelo, but it certainly is cool.

7. Are there any differences between the channels except the reverb and trem?

8. To get the internals out, it seems i need to remove the 4 screws on the top. But also seems i need to hold those nuts way up in the cabinet also. Any tips on that? I was thinking a socket with a pretty big extension.

9. Getting an odd light rattle at medium volumes. I am guessing it is someing loose inside. Any common culprits?

I do love this amp, and I probably will spend the money to get it recapped and the like at some point to make it a good, reliable giging amp. I thought the cleans on my Crate VC5212 were great (they are, and have had many people comment on this) but compared to the MM....wow. It sounds terrible... because these amps are just that great. I was playing chords on my tele and the tone of just basic chords being strummed moved me emotionally. Its just insane the sound on this.