Since it's this little guy's "last chance", I'd do some root pruning. It can't hurt and it very well could help. Dig him up and remove about an inch from all visible roots (you may have to wash or bare root the plant). Re-plant in suitable soil away from any other root competition (larger, more aggressive plants). You can amend the planting area with some Dr. Earth starter fertilizer, which is formulated to stimulate root production, or a similar root booster product. This is NOT the same as B1, although that may be a component of the mix. B1 has no impact on root development and is typically present in the soil in sufficient concentration anyway.

Fall fertilizing of woody plants is highly recommended. It is a period of very active root development. You just want to avoid any high nitrogen fertilizers that may encourage rapid new growth at that time of year, so focus on the second two numbers of the fert label being higher than the first. Root pruning will encourage the development of fine feeder roots, which will be more able to support topgrowth.

Chlorosis is an indication of insufficiently acidic soil withholding needed nutrients. Make sure your soil is appropriately acidic before planting.

Trimming back topgrowth does not really stimulate root development. In fact, pruning encourages additional growth so trimming back the above ground portions of the plant can place unnecessary stress on an already overtaxed root system!