Guitar player finding problems with borrowed bass

There's a song in the band I want to do but the singer/bass player said he couldn't do both on that song at the same time. I've been wanting to do this song for 2 years so I offered to play bass. He loaned me his old, beat-up 4-string Ibanez to practice at home. The strings were literally rusted so I:

Chopped the strings off
Taped the fretboard
Sanded the discoloration off all 22 frets
Lemon-oiled the fretboard
Hydrated the fretboard with mineral oil
Cleaned & polished all but the fretboard and hardware

That was Sunday. I researched Ibanez to find there 4-string basses have a standard string gauge 45-68-80-100. Therefore I went to GC and bought a two pack of D'Addario EL170TP regular lights. On the package it said they're brighter sounding than nickel plated steel. I emailed D'Addario and they said the strings are NPS's but brighter sounding.

I put graphite in the nut slots & bridge and strung it up. My first ever bass stringing. Seemed just like guitar stringing on a meatier level. I think I only wrapped once thinking they're all wound strings and grab well and wanted to have less wraps for less stretch. I tuned/stretched/tuned/stretched then played My Sharona through my Fender HRD guitar amp. The low E string is much louder and mushier than any other strings. When I'm playing the G octaves the low G sounds pissed off and the high one is not as loud.

I see the T-risers (whatever they're called—individual bridge piece) are funky. The one for the low is on like a 45-degree angle where the upper side is really low. Is that low action on the low E causing it to be louder than the rest of the strings?

I've never done an intonation on guitar or bass but I'm seriously thinking about spinning some of those allen screws on the T-risers to lower the action. It's too high on most of the strings. And I'm thinking about raising that one side of the low E T-riser. Any of you bass players out there have any ideas, suggestions or comments?

Lastly, I was thinking about cutting these strings off and put regular NPS strings (GHS ML3045 baby boomers regular light NPS 45-68-80-100) to get a mellower tone. That is, unless the D'Addarios will mellow out in a few hours of playing. :shock:

Summary of questions:
1. Is the "clankyness" of the strings the frets due to the super bright strings or normal with new bass strings?
2. Why is the low E louder than other strings?
3. Will playing this 4-string bass through my Fender tube amp damage it?
4. Should I jump on it and adjust the T-bar things up/down to my like of action at the expense of actual intonation? I don't know if it makes a big deal on bass.