I'd get a new chain and check the hanger alignment. If the chain skips on one or more cogs while pedaling under a heavy load, a new cassette will also be needed.

About the ergo lever, getting the last piece into position can be tough. I always mount a 5mm hex wrench in a vise and use it to hold the ergo lever by the end of the main pivot shaft. That shaft must be held stationary, so pushing on the spring coil bushing does not allow the shaft to be pushed down. The thumb lever spring can be pushed to the side with the bushing, to let the bushing engage the pivot shaft. I've temporarily installed the center fixing bolt, just to hold the bushing in place, then installed the big wind-up spring. The tail of the spring can be slipped under the fixing bolt, then the other end swung around to the post on the g-spring retainer. It is the toughest part of the job. The new ultrashift levers are MUCH easier to work on, but the don't come in 9 speed.

Since you have a triple with a 13-29, you must have a long cage RD, not a medium cage. I tried that with a medium cage and could not avoid contact between the 29T cog and top pulley. Make the chain as long as possible. If you have a typical 52/42/30, set the length in the little ring and smallset cog, to the longest that causes the lower pulley to swing forward a bit and produce some chain tension. If you have a smaller little ring, you should expect chain sag with at least a couple of the smallest cogs and little ring.