I did the exact same EK to UA connection about 18 months ago - T1 and T3 are connected, so it's a quick walk. I actually did UA OLCI before leaving BLR just in case they wanted to see an onward boarding pass in order to go through flight connections in DXB and re-enter the secure boarding area (instead of making you enter UAE and then come back again). As it turned out, they didn't ask me for it - but you may want to do it anyways so you wouldn't be stuck having to exit the airport and wait for the UA ticket counter to open.

Re: lounge, the only option is the LH lounge near gate 128-129 (I believe) - was just there a few days ago and the food was pretty good, but the internet is quite slow.

Hope this helps! PM me if you have any more questions.